Virus vectors and methods of making and administering the same

ABSTRACT

The present invention provides genetically-engineered parvovirus capsids and viruses designed to introduce a heterologous gene into a target cell. The parvoviruses of the invention provide a repertoire of vectors with altered antigenic properties, packaging capabilities, and/or cellular tropisms as compared with current AAV vectors.

RELATED APPLICATION INFORMATION

This application is a divisional of co-pending U.S. patent applicationSer. No. 10/205,942, filed Jul. 26, 2002, which is a divisional of U.S.patent application Ser. No. 09/438,268, filed Nov. 10,1999 (now U.S.Pat. No. 6,491,907), which claims the benefit of U.S. ProvisionalApplication Ser. No. 60/107,840, filed Nov. 10,1998, and Ser. No.60/123,651, filed Mar. 10, 1999, which are incorporated herein byreference in their entireties.

STATEMENT OF FEDERAL SUPPORT

This invention was made, in part, with government support under grantnumbers DK42701 and 5-32938 0-110 from the National Institutes ofHealth. The United States government has certain rights to thisinvention.

FIELD OF THE INVENTION

The present invention relates to virus vectors, in particular, modifiedparvovirus vectors and methods of making and administering the same.

BACKGROUND

Parvoviruses are small, single-stranded, non-enveloped DNA virusesbetween twenty to thirty nanometers in diameter. The genomes ofparvoviruses are approximately 5000 nucleotides long, containing twoopen reading frames. The left-hand open reading frame codes for theproteins responsible for replication (Rep), while the right-hand openreading frame encodes the structural proteins of the capsid (Cap). Allparvoviruses have virions with icosahedral symmetry composed of a majorCap protein, usually the smallest of the Cap proteins, and one or twominor Cap proteins. The Cap proteins are generated from a single genethat initiates translation from different start codons. These proteinshave identical C-termini, but possess unique N-termini due to differentinitiation codons.

Most parvoviruses have narrow host ranges; the tropism of B19 is forhuman erythroid cells (Munshi et al., (1993) J. Virology 67:562), whilecanine parvovirus has a tropism for lymphocytes in adult dogs (Parrishet al., (1988) Virology 166:293; Chang et al., (1992) J. Virology66:6858). Adeno-associated virus, on the other hand, can replicate wellin canine, mouse, chicken, bovine, monkey, as well as numerous humanlines, when the appropriate helper virus is present. In the absence ofhelper virus, AAV will infect and establish latency in all of these celltypes, suggesting that the AAV receptor is common and conserved amongspecies. Several serotypes of AAV have been identified, includingserotypes 1, 2, 3, 4, 5 and 6.

Adeno-associated virus (AAV) is a dependent parvovirus twenty nanometersin size which requires co-infection with another virus (eitheradenovirus or certain members of the herpes virus group) to undergo aproductive infection in cultured cells. In the absence of co-infectionwith helper virus, the AAV virion binds to a cellular receptor andenters the cell, migrating to the nucleus, and delivers asingle-stranded DNA genome that can establish latency by integrationinto the host chromosome. The interest in AAV as a vector has centeredaround the biology of this virus. In addition to its unique life-cycle,AAV has a broad host range for infectivity (human, mouse, monkey, dog,etc.), is ubiquitous in humans, and is completely nonpathogenic. Thefinite packaging capacity of this virus (4.5 kb) has restricted the useof this vector in the past to small genes or cDNAs. To advance theprospects of AAV gene delivery, vectors sufficient to carry larger genesmust be developed. In addition, virions that specifically andefficiently target defined cell types without transducing others will berequired for clinical application.

The capsid proteins of AAV2 are Vp1, 2, and 3 with molecular weights of87, 73, and 62 kDa, respectively. Vp3 represents nearly 80% of the totalprotein in intact virions, while Vp1 and Vp2 represent 10% each(Muzyczka, (1992) Curr. Topics Microbiol. Immunol. 158:97; Rolling etal., (1995) Molec. Biotech. 3:9; Wistuba et al. (1997) J. Virology71:1341). Early studies of AAV2 support that all three capsid subunitsare required to extract single stranded genomes from the pool ofreplicating double stranded DNA. These genomes are then sequestered intopreformed immature particles that maturate to infectious particles.These particles have a density between 1.32 and 1.41 g/mL in cesiumchloride and sediment between 60S and 125S in sucrose (Myers et al.,(1981) J. Biological Chem. 256:567; Myers et al., (1980) J. Virology35:65).

Previous mutagenesis studies of AAV2 capsids have shown that insertionsand deletions in the Vp3 domain completely inhibit the accumulation ofsingle stranded virions and production of infectious particles (Hermonatet al, (1984) J. Virology 51:329; Ruffing et al., (1992) J. Virology66:6922). Yang et al., (1998) Human Gene Therapy 9:1929, have reportedthe insertion of a sequence encoding the variable region of a singlechain antibody against human CD34 at the 5′ end of the AAV2 Vp1, Vp2 orVp3 coding regions. These investigators observed extremely lowtransduction of CD34 expressing KG-1 cells by AAV virions containing theVp2 fusion protein (1.9 transducing units/ml or less, sentence spanningpages 1934-35). KG-1 cells are reportedly not permissive to infection bya wild-type rAAV vector. These results with the Vp2 fusion AAV aresuspect as transduction of KG-1 cells by this virus was essentiallyinsensitive to an anti-AAV capsid antibody (430 vs. 310 transducingunits/ml; Table 2), whereas transduction of HeLa cells was markedlyreduced by this antibody (63,2000 vs. <200 transducing units/ml; Table2). No characterization of the putative fusion virions was undertaken toconfirm that the particles contained the Vp2 fusion protein, theantibody was expressed on the capsid surface, or that the particlesbound CD34 proteins. In addition, rAAV particles could only be producedif all three wild-type capsid subunits were provided, in addition to thechimeric subunit (Page 1934, Col. 2, lines 5-12). Collectively, theseresults suggest the chimeric subunits were not incorporated into viableAAV particles, and the low level of chimeric protein observed in targetcells was, in fact, due to cellular uptake of chimeric capsid protein orprotein aggregates by other mechanisms.

Several studies have demonstrated that parvovirus capsid proteins can bemutated and virion assembly studied. In one study, the coding region for147 amino acids of the hen egg white lysozyme was substituted for B19Vp1 unique coding sequence. This modification resulted in purified emptyparticles that retained lysozyme enzymatic activity (Miyamura et al,(1994) Proc. Nat. Acad. Sci. USA 91:8507). In addition, expression ofpeptides (9 and 13 residues) in B19 Vp2 resulted in empty particles thatwere immunogenic in mice supporting surface presentation of theinsertions (Brown et al., (1994) Virology 198:477). In a more recentstudy, the CD8+CTL epitope (residues 118-132) against lymphocyticchoriomeningitis virus (LCMV) nucleoprotein was inserted into the Vp2capsid protein of porcine parvovirus (ppv) (Sedlik et al., (1997) Proc.Nat. Acad. Sci. USA 94:7503). This capsid protein, with the epitopecloned at the N-terminus, self-assembled when expressed in a baculovirussystem. This chimeric virus-like particle was then used to immunize miceagainst a lethal challenge from LCMV. While these studies evaluatedcapsid structure and assembly, they did not address the issue ofpackaging B19 genomes into the altered capsids.

Recombinant (r)AAV vectors require only the inverted terminal repeatsequences in cis of the 4679 bases to generate virus. All other viralsequences are dispensable and may be supplied in trans (Muzyczka, (1992)Curr. Topics Microbiol. Immunol. 158:97). Attractive characteristics ofAAV vectors for gene therapy are the stability, genetic simplicity, andease of genetic manipulation of this virus. While each of these factorsremains valid, some obstacles to the application of rAAV vectors haverecently come to light. These include inefficiency of vectortransduction and packaging constraints. It is not surprising, given thecryptic nature of this virus, that new insights into its biology havesurfaced only after extensive research with rAAV vectors, which are moreeasily assayed compared with wild-type AAV.

With respect to the efficiency of vector transduction, several recentstudies have shown great promise in terms of duration of transgeneexpression in vivo; however, there has been a shortfall in theefficiency of transduction, which was unexpected based on previousresults in vitro (Flotte et al., (1993) Proc. Nat. Acad. Sci. USA90:10613). One of the first experiments in rodents to demonstrate theutility of rAAV vectors in vivo was aimed at transduction of braintissue in rat (Kaplitt et al., (1994) Nature Genet. 7:148). In additionto brain, muscle has been found to be efficiently transduced in vivo byAAV vectors, demonstrating long term gene expression (at least 1.5years), lack of immune response, and no vector toxicity (Xiao et al.,(1996) J. Virol. 70:8098; Clark et al., (1996) Hum. Gene Ther. 8:659;Fisher et al., (1997) Nat. Med. 3:306; Monahan et al, (1998) Gene Ther.5:40). The primary steps that influence efficient vector delivery arevirus entry and conversion of second strand synthesis (see Ferrari etal, (1996) J. Virology 70:3227-34).

The overall success of AAV as a general-purpose viral vector depends onthe ability to package larger than full-length AAV genomes (5 kb) intorAAV vectors. Studies by Dong et al., (1996) Hum. Gene Ther. 7:2101,have determined the packaging limitations using rAAV vectors as between104% and 108%. This packaging restriction precludes the use of a numberof important genes currently being tested for human gene therapy (e.g.,the dystrophin gene or current mini-dystrophin constructs).

Accordingly, there remains a need in the art for improved virus vectorswith greater packaging limits and transduction efficiency than AAVvectors. In addition, there remains a need for virus vectors withaltered tropisms as compared with AAV vectors.

SUMMARY OF THE INVENTION

The present invention provides parvovirus vectors for introducing (i.e.,delivering) and, preferably, expressing a nucleotide sequence in a cell.The invention is based, in part, on the discovery that parvovirusvectors possessing unique structures and characteristics as comparedwith current vectors may be created by substituting or inserting aforeign sequence (i.e., an exogenous amino acid sequence) into aparvovirus capsid. The invention further provides novel vectors that aregenerated by cross-packaging a parvovirus genome (preferably, an AAVgenome) within a different parvovirus capsid. The present inventionprovides a repertoire of novel parvovirus vectors that may possessunique and advantageous antigenic properties, packaging capabilities,and cellular tropisms as compared with current AAV vectors.

These and other aspects of the invention are set forth in more detail inthe description of the invention below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the insertional mutagenesis strategy for the AAV2 capsid. Acassette containing the Kan^(r) gene flanked by EcoRV and Nae I siteswere cloned into the plasmid pAV2Cap. pAV2Cap, which contains the openreading frame of AAV2 capsid, was partially digested with Hae III, NlaIV, and Rsa I separately so that unit length products were isolated. The43 positions of restriction sites for these enzymes are shown above thediagram of the capsid open reading frame. The position of the Kan^(r)insert was mapped by restriction enzyme digestion and in some casessequenced. Once the position was determined the Kan^(r) gene was removedby EcoRV digestion, and the capsid domain subcloned into pACG. Thisstrategy resulted in inserting a 12 base pair fragment, with half Nae Isites flanking a unique Eco RV site, into the respective Hae III, NlaIV, and Rsa I sites. The twelve base pairs code for four amino acids oneof which is shown above the diagram of pACG2.

FIG. 2 shows the expression of capsid proteins in cells transfected withwild-type and insertion mutant helper plasmids of pACG2. Cell lysatesfrom 293 cells transfected with 1, H2285; 2, H2634; 3, H2690; 4, N2944;5, H2944; 6, H3595; 7, H4047; 8, wild-type were analyzed by acrylamidegel electrophoresis and immunoblotting with the B1 monoclonal antibodyand detected by peroxidase-conjugated secondary antibody. On the left ofthe Western blot are the positions of the molecular weight standards andon the right are the positions of the major capsid protein, VP3 and theminor capsid proteins VP2 and VP1.

FIG. 3 shows expression of a Lac Z transgene in cells infected withinsertion mutant or wild-type virus. Panel A. Dot blot hybridization tothe Lac Z transgene. Cell lysates of adenovirus infected 293 cellstransfected with the insertion mutant or wild-type helper plasmids andthe Lac Z transgene containing vector were subjected to cesium chlorideisopycnic gradient. Fractions from the gradient were treated with DNaseand RNase prior to dot blotting to remove unpackaged nucleic acids,fraction numbers are labeled above the dot blot. Fraction 1 has adensity range of 1.377-1.41, fraction 2 has a density range of1.39-1.435, and fraction 3 has a density range of 1.42-1.45. Theβ-galactosidase gene was used as the control template, to estimateparticle numbers. Estimates of particle number where derived assuming 1μg of 1000 bp DNA has 9.1×10¹¹ molecules. Panel B. Infection of HeLacells with 1.75×10⁸ particles from various insertion mutants andwild-type capsid containing the Lac Z transgene. Cells expressing thetransgene appear blue when stained with X-gal.

FIG. 4 shows characterization of the insertion mutants using electronmicroscopy. 200 uL samples of each virus from peak fraction of gradientwere dialyzed against 1×PBS+1 mM MgCl₂ and speed-vac desiccated, thenresuspended in 20 uL of distilled H₂O. Samples were negative stainedwith 2% phosphotungstic acid. Panel A. rAAV2 with wild-type virion.Infectious insertion viruses H2690 (Panel B), and H2591 (Panel C).Non-infectious viruses H2285 (Panel D), H2634 (Panel E) and, H3595(Panel F). The black bar is 100 nm; the magnification is equivalent ineach panel.

FIG. 5 presents analysis of virion composition from wild-type andvarious insertion mutant viruses isolated from cell lysates by cesiumchloride gradient centrifugation. Peak fractions of virus weredetermined by dot blot hybridization and dialyzed against 1×PBS+1 mMMgCl₂. For each, viral sample between 1.0×10⁹ and 2.5×10⁹ particles wereused. Virions from 1. Wild-type rAAV2; 2. H2285; 3. R2349; 4. H2591; 5.H2634; 6. H2690; 7. H3766; and 8. N4160 were analyzed by acrylamide gelelectrophoresis and immunoblotting with the B1 monoclonal antibody anddetected by peroxidase-conjugated secondary antibody. On the left of theWestern blot are the positions of the molecular weight standards and onthe right are the positions of the major capsid protein, VP3 and theminor capsid proteins VP2 and VP1.

FIG. 6 shows the analysis of wild-type and non-infectious insertionmutant virus batch binding to heparin agarose by dot blot hybridization.Viruses with wild-type virions and insertion in the capsids weredialysed against 0.5×PBS and 0.5 mM MgCl₂. One hundred microliters ofeach virus was bound to 100 μl of heparin agarose, at room temperaturefor one hour. Samples were washed six times with 500 μl of wash buffereach, followed by elution with 100 μl of 0.5, 1.0 and 1.5M NaCl each,and the supernatant from each wash and elution step was saved. Twentymicroliters of supernatant from each step and 20 μl of the agarosepellet were used for dot blot hybridization. Pairs of washes werecombined and 1/50 of the total volume from each pair was used for dotblot hybridization, while one fifth of the elution supernatant andagarose bed volumes were used. The 100% bound was equivalent to onefifth of the virus added to the heparin agarose. Samples 1. rAAV2 withwild-type virion; 2. H2285; 3. H2416; 4. H2634; and 5. H3761.

FIG. 7 is schematic representation of the AAV2/4 subunit chimeras.

FIG. 8 is a diagram of the helper plasmid pAAV2/B19p2Cap. The codingregion of the B19 major structural protein, Vp2, was seamlessly clonedfrom AAV-Vp3 to TM.

FIG. 9 provides EM analysis of chimeric virus particles produced withpAAV/B19Vp2Cap.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides parvovirus vectors for the delivery ofnucleic acids to cells, both in vitro and in vivo. Alternatively, theinvention provides novel capsid structures for use, e.g., as vaccines orfor delivery of compounds to cells (e.g., as described by U.S. Pat. No.5,863,541 to Samulski et al., the disclosure of which is incorporatedherein by reference in its entirety). The parvovirus vectors of thepresent invention utilize the advantageous properties of AAV vectors,and may mitigate some of the problems encountered with these vectors. Inparticular embodiments, the parvovirus vectors may possess different oraltered characteristics from AAV vectors, including but not limited to,antigenic properties, packaging capabilities, and/or cellular tropism.

The term “parvovirus” as used herein encompasses all parvoviruses,including autonomously-replicating parvoviruses and dependoviruses. Theautonomous parvoviruses include members of the genera Parvovirus,Erythrovirus, Densovirus, Iteravirus, and Contravirus. Exemplaryautonomous parvoviruses include, but are not limited to, mouse minutevirus, bovine parvovirus, canine parvovirus, chicken parvovirus, felinepanleukopenia virus, feline parvovirus, goose parvovirus, and B19 virus.Other autonomous parvoviruses are known to those skilled in the art.See, e.g., BERNARD N. FIELDS et al., VIROLOGY, volume 2, chapter 69 (3ded., Lippincott-Raven Publishers).

The genus Dependovirus contains the adeno-associated viruses (AAV),including but not limited to, AAV type 1, AAV type 2, AAV type 3, AAVtype 4, AAV type 5, AAV type 6, avian AAV, bovine AAV, canine AAV,equine AAV, and ovine AAV. See, e.g., BERNARD N. FIELDS et al.,VIROLOGY, volume 2, chapter 69 (3d ed., Lippincott-Raven Publishers).

The parvovirus particles, capsids and genomes of the present inventionare preferably from AAV.

The term “tropism” as used herein refers to entry of the virus into thecell, optionally and preferably, followed by expression of sequencescarried by the viral genome in the cell, e.g., for a recombinant virus,expression of the heterologous nucleotide sequences(s). Those skilled inthe art will appreciate that transcription of a heterologous nucleicacid sequence from the viral genome may not be initiated in the absenceof trans-acting factors, e.g., for an inducible promoter or otherwiseregulated nucleic acid sequence. In the case of AAV, gene expressionfrom the viral genome may be from a stably integrated provirus, from anon-integrated episome, as well as any other form in which the virus maytake within the cell.

The parvovirus vectors of the present invention are useful for thedelivery of nucleic acids to cells both in vitro and in vivo. Inparticular, the inventive vectors may be advantageously employed todeliver or transfer nucleic acids to animal cells. Nucleic acids ofinterest include nucleic acids encoding peptides and proteins,preferably therapeutic (e.g., for medical or veterinary uses) orimmunogenic (e.g., for vaccines) peptides or proteins.

A “therapeutic” peptide or protein is a peptide or protein that mayalleviate or reduce symptoms that result from an absence or defect in aprotein in a cell or subject. Alternatively, a “therapeutic” peptide orprotein is one that otherwise confers a benefit to a subject, e.g.,anti-cancer effects. Therapeutic peptides and proteins include, but arenot limited to, CFTR (cystic fibrosis transmembrane regulator protein),dystrophin (including the protein product of dystrophin mini-genes, see,e.g, Vincent et al., (1993) Nature Genetics 5:130), utrophin (Tinsley etal., (1996) Nature 384:349), clotting factors (Factor XIII, Factor IX,Factor X, etc.), erythropoietin, the LDL receptor, lipoprotein lipase,ornithine transcarbamylase, β-globin, α-globin, spectrin, α-antitrypsin,adenosine deaminase, hypoxanthine guanine phosphoribosyl transferase,β-glucocerebrosidase, sphingomyelinase, lysosomal hexosaminidase,branched-chain keto acid dehydrogenase, hormones, growth factors (e.g.,insulin-like growth factors 1 and 2, platelet derived growth factor,epidermal growth factor, nerve growth factor, neurotrophic factor-3 and-4, brain-derived neurotrophic factor, glial derived growth factor,transforming growth factor-α and -β, and the like), cytokines (e.g.,α-interferon, β-interferon, interferon-γ, interleukin-2, interleukin-4,interleukin 12, granulocyte-macrophage colony stimulating factor,lymphotoxin), suicide gene products (e.g., herpes simplex virusthymidine kinase, cytosine deaminase, diphtheria toxin, cytochrome P450,deoxycytidine kinase, and tumor necrosis factor), proteins conferringresistance to a drug used in cancer therapy, tumor suppressor geneproducts (e.g., p53, Rb, Wt-1, NF1, VHL, APC, and the like), and anyother peptide or protein that has a therapeutic effect in a subject inneed thereof.

Further exemplary therapeutic peptides or proteins include those thatmay used in the treatment of a disease condition including, but notlimited to, cystic fibrosis (and other diseases of the lung), hemophiliaA, hemophilia B, thalassemia, anemia and other blood disorders, AIDS,Alzheimer's disease, Parkinson's disease, Huntington's disease,amyotrophic lateral sclerosis, epilepsy, and other neurologicaldisorders, cancer, diabetes mellitus, muscular dystrophies (e.g.,Duchenne, Becker), Gaucher's disease, Hurler's disease, adenosinedeaminase deficiency, glycogen storage diseases and other metabolicdefects, retinal degenerative diseases (and other diseases of the eye),and diseases of solid organs (e.g., brain, liver, kidney, heart).

The present invention also provides vectors useful as vaccines. The useof parvoviruses as vaccines is known in the art (see, e.g., Miyamura etal, (1994) Proc. Nat. Acad. Sci USA 91:8507; U.S. Pat. No. 5,916,563 toYoung et al., U.S. Pat. No. 5,905,040 to Mazzara et al., U.S. Pat. No.5,882,652, U.S. Pat. No. 5,863,541 to Samulski et al; the disclosures ofwhich are incorporated herein in their entirety by reference). Theantigen may be presented in the parvovirus capsid, as described belowfor chimeric and modified parvovirus vectors. Alternatively, the antigenmay be expressed from a heterologous nucleic acid introduced into arecombinant AAV genome and carried by the inventive parvoviruses. Anyimmunogen of interest may be provided by the parvovirus vector.Immunogens of interest are well-known in the art and include, but arenot limited to, immunogens from human immunodeficiency virus, influenzavirus, gag proteins, tumor antigens, cancer antigens, bacterialantigens, viral antigens, and the like.

As a further alternative, the heterologous nucleic acid sequence mayencode a reporter peptide or protein (e.g., an enzyme). Reporterproteins are known in the art and include, but are not limited to, GreenFluorescent Protein, β-galactosidase, alkaline phosphatase,chloramphenicol acetyltransferase, and the like.

Alternatively, in particular embodiments of the invention, the nucleicacid of interest may encode an antisense nucleic acid, a ribozyme (e.g.,as described in U.S. Pat. No. 5,877,022), RNAs that effectspliceosome-mediated trans-splicing (Puftaraju et al., (1999) NatureBiotech. 17:246), or other non-translated RNAs, such as “guide” RNAs(Gorman et al., (1998) Proc. Nat. Acad. Sci. USA 95:4929; U.S. Pat. No.5,869,248 to Yuan et al.), and the like.

Except as otherwise indicated, standard methods known to those skilledin the art may be used for the construction of rAAV genomes,transcomplementing packaging vectors, transiently and stably transfectedpackaging cells according to the present invention. Such techniques areknown to those skilled in the art. See, e.g., SAMBROOK et al., MOLECULARCLONING: A LABORATORY MANUAL 2nd Ed. (Cold Spring Harbor, N.Y., 1989);F. M. AUSUBEL et al. CURRENT PROTOCOLS IN MOLECULAR BIOLOGY (GreenPublishing Associates, Inc. and John Wiley & Sons, Inc., New York).

1. Hybrid Viruses.

The hybrid parvovirus vectors of the present invention may overcome someof the disadvantages of AAV vectors for delivery of nucleic acids orother molecules to cells.

A “hybrid” parvovirus, as used herein, is an AAV genome encapsidatedwithin a different (i.e., another, foreign, exogenous) parvoviruscapsid. Alternatively stated, a hybrid parvovirus has a parvovirusgenome encapsidated within a different parvovirus capsid. As usedherein, by “different” it is intended that the AAV genome is packagedwithin another parvovirus capsid, e.g., the parvovirus capsid is fromanother AAV serotype or from an autonomous parvovirus.

Preferably, the parvovirus genome is an AAV genome (preferably arecombinant AAV genome). It is also preferred that the AAV genomecomprises one or more AAV inverted terminal repeat(s) as describedbelow. Typically, as described in more detail below, a recombinant AAV(rAAV) genome will retain only those elements required in cis (e.g., oneor more AAV ITRs), with the rest of the genome (e.g., the rep/cap genes)being provided in trans.

In particular preferred embodiments the parvovirus capsid is an AAVcapsid (i.e., a hybrid AAV vector). According to this embodiment, theAAV capsid packages an AAV genome of a different serotype (andpreferably, of a different serotype from the one or more AAV ITRs). Forexample, a recombinant AAV type 1, 2, 3, 4, 5 or 6 genome may beencapsidated within an AAV type 1, 2, 3, 4, 5 or 6 capsid, provided thatthe AAV capsid and genome (and preferably, the one or more AAV ITRs) areof different serotypes.

Illustrative hybrid parvoviruses according to the present invention arean AAV type 2 genome packaged within an AAV type 1, 3, 4, 5 or 6 capsid.In particular preferred embodiments, the hybrid parvovirus comprises anAAV type 3, type 4, or type 5 capsid packaging an AAV type 2 genome,more preferably, an AAV type 3 or type 5 capsid packaging a type 2genome.

In other preferred embodiments, an AAV type 1, 3, 4, 5 or 6 genome ispackaged within a different AAV capsid (e.g., a type 1 genome in a type2, 3, 4, 5, or 6 capsid, and the like).

Also preferred are hybrid B19/AAV parvoviruses in which an AAV genome(e.g., an AAV type 1, 2, 3, 4, 5 or 6 genome) is packaged within a B19capsid. More preferably, the hybrid parvovirus has a B19 capsid and anAAV type 2 genome.

Further preferred are hybrid parvoviruses in which a mouse minute virus,bovine parvovirus, canine parvovirus, chicken parvovirus, felinepanleukopenia virus, feline parvovirus, or goose parvovirus capsidpackages an AAV genome, more preferably an AAV type 2 genome.

Specific hybrid viruses include those having the capsid sequence encodedby nucleotides 2123 to 4341 of SEQ ID NO:1. This sequence encodes theAAV2 rep genes and AAV4 capsid in a pBluescript backbone. It is alsopreferred that the hybrid parvovirus having the capsid sequence given bySEQ ID NO:1 is an AAV2 genome. Alternatively, the nucleotide sequence ofthe AAV4 capsid is substantially homologous to the nucleotide sequencegiven as nucleotides 2123 to 4341 of SEQ ID NO:1. As a furtheralternative, the nucleotide sequence of the AAV4 capsid encodes theamino acid sequence encoded by nucleotides 2123 to 4341 in SEQ ID NO:1.The term “substantially homologous” is as defined hereinbelow.

One of the limitations of current AAV vectors for gene delivery is theprevalence of neutralizing antibodies against AAV within the humanpopulation. For example, it is estimated that 80% of adults areseropositive for AAV type 2. In preferred embodiments, the instantinvention provides hybrid parvovirus vectors that may be advantageouslyemployed to reduce (e.g., diminish, decrease, mitigate, and the like) animmune response in the subject being treated. Thus, for example, a rAAVtype 2 vector genome carrying a heterologous nucleic acid sequence orsequences may be packaged within an AAV type 3 capsid and administeredto a subject who is seropositive for AAV type 2 and cannot neutralizeAAV type 3 virus.

According to this aspect of the invention, a rAAV genome may be packagedwithin any non-homologous parvovirus capsid for delivery to a cell, invitro or in vivo. In preferred embodiments, the AAV genome is packagedwithin an array of non-homologous capsids to overcome neutralizingantibodies and/or or to prevent the development of an immune response.In particular preferred embodiments, the rAAV may be delivered within aseries of hybrid virus particles, so as to continually present theimmune system with a new virus vector. This strategy will allow forrepeated administration without immune clearance.

A further limitation encountered with AAV vectors concerns the cellulartropism of this virus. The wild-type tropism of AAV is problematic bothbecause AAV infects a wide range of cell types and because it exhibitsno infectivity in other potential target cells of interest (e.g,erythroid cells). Autonomous parvoviruses, in contrast, have a narrowercellular tropism. The tropisms of particular autonomous parvoviruses areknown to those skilled in the art. Illustrative cellular tropisms ofautonomous parvoviruses include: B19 virus (erythroid cells), canineparvovirus (gut epithelium), MVM(p) (fibroblasts); and goose parvovirus(myocardial lining of the heart). Furthermore, autonomous parvovirusesexhibit a wider range of host species than does AAV, whichcharacteristic may be utilized to develop AAV vectors for administrationto bovines, canines, felines, geese, ducks, and the like, e.g., forveterinary treatments. Thus, cross-packaging of AAV genomes inautonomous parvovirus capsids according to the present invention may beutilized to produce a virus vector with a different cellular tropismthan AAV.

With respect to AAV/AAV hybrids, all of the AAV serotypes infect a broadhost range of cells. However, there are differences in the rates ofvector transduction, suggesting that the different serotypes may usedifferent cellular receptors. In addition, only limited competition isobserved among serotypes in binding experiments, which observationfurther indicates that the different serotypes have evolved to usedistinct receptors (Mizukami et al., (1996) Virology 217:124).Accordingly, hybrid parvoviruses of the present invention that packagean AAV genome in an AAV capsid of a different serotype also provideopportunities for delivering AAV vectors to a wider range of cell typesthan current AAV vectors and/or for directing AAV vectors to specifictarget cells.

In preferred embodiments, the hybrid parvovirus particle contains a rAAVgenome. As used herein, the rAAV genome carries at least oneheterologous nucleic acid sequence to be delivered to a cell. Thoseskilled in the art will appreciate that the rAAV genome can encode morethan one heterologous nucleic acid sequence (e.g., two, three or moreheterologous nucleic acid sequences), generally only limited by thepackaging capacity of the virus capsid. Heterologous nucleic acidsequence(s) of interest for use according to the present invention areas described above.

As used herein, a recombinant hybrid parvovirus particle encompassesvirus particles with hybrid, chimeric, targeted and/or modifiedparvovirus capsids as described hereinbelow. Moreover, those skilled inthe art will understand that the parvovirus capsid may include othermodifications or mutations (e.g., deletion, insertion, point and/ormissense mutations, and the like). Likewise, the rAAV genome may includemodifications or mutations (e.g., deletion, insertion, point and/ormissense mutations, and the like). Those skilled in the art will furtherappreciate that mutations may incidentally be introduced into the rAAVgenome or parvovirus capsid as a result of the cloning strategyemployed.

The rAAV genome of the hybrid parvovirus preferably encodes at least oneAAV inverted terminal repeat (ITR), preferably two AAV ITRs, and morepreferably two homologous AAV ITRs, which flank the heterologous nucleicacid sequence(s) to be delivered to the cell. The AAV ITR(s) may be fromany AAV, with types 1, 2, 3, 4, 5 and 6 being preferred, and type 2being most preferred. The term “inverted terminal repeat” includessynthetic sequences that function as an AAV inverted terminal repeat,such as the “double-D sequence” as described in U.S. Pat. No. 5,478,745to Samulski et al., the disclosure of which is incorporated in itsentirety herein by reference. It has been demonstrated that only asingle 165 bp double-D sequence is required in cis for site specificintegration, replication, and encapsidation of vector sequences. AAVITRs according to the present invention need not have a wild-type ITRsequence (e.g., a wild-type sequence may be altered by insertion,deletion, truncation or missense mutations), as long as the ITRfunctions to mediate virus packaging, replication, integration, and/orprovirus rescue, and the like.

In hybrid parvoviruses according to the present invention, the AAVITR(s) is different from the parvovirus capsid. Moreover, if the capsidis an AAV capsid, the capsid and the ITR(s) are of different AAVserotypes. In preferred embodiments, the AAV ITR(s) is from AAV type 2and the parvovirus capsid is an AAV type 3, 4 or 5 capsid, morepreferably an AAV type 3 or 5 capsid. In alternate preferredembodiments, the hybrid parvovirus has a B19 capsid and the AAV ITR(s)is from AAV type 2.

The rAAV genomes of the invention may additionally contain expressioncontrol elements, such as transcription/translation control signals,origins of replication, polyadenylation signals, and internal ribosomeentry sites (IRES), promoters, enhancers, and the like, operablyassociated with the heterologous nucleic acid sequence(s) to bedelivered to the cell. Those skilled in the art will appreciate that avariety of promoter/enhancer elements may be used depending on the leveland tissue-specific expression desired. The promoter/enhancer may beconstitutive or inducible, depending on the pattern of expressiondesired. The promoter/enhancer may be native or foreign and can be anatural or a synthetic sequence. By foreign, it is intended that thepromoter/enhancer region is not found in the wild-type host into whichthe promoter/enhancer region is introduced.

Promoters/enhancers that are native to the target cell or subject to betreated are most preferred. Also preferred are promoters/enhancers thatare native to the heterologous nucleic acid sequence. Thepromoter/enhancer is chosen so that it will function in the targetcell(s) of interest. Mammalian promoters/enhancers are also preferred.

Inducible expression control elements are preferred in thoseapplications in which it is desirable to provide regulation overexpression of the heterologous nucleic acid sequence(s). Induciblepromoters/enhancer elements for gene delivery are preferablytissue-specific promoter/enhancer elements, and include muscle specific(including cardiac, skeletal and/or smooth muscle), neural tissuespecific (including brain-specific), liver specific, bone marrowspecific, pancreatic specific, spleen specific, retinal specific, andlung specific promoter/enhancer elements. Other induciblepromoter/enhancer elements include hormone-inducible and metal-inducibleelements. Exemplary inducible promoters/enhancer elements include, butare not limited to, a Tet on/off element, a RU486-inducible promoter, anecdysone-inducible promoter, a rapamycin-inducible promoter, and ametalothionein promoter.

In embodiments of the invention in which the heterologous nucleic acidsequence(s) will be transcribed and then translated in the target cells,specific initiation signals are generally required for efficienttranslation of inserted protein coding sequences. These exogenoustranslational control sequences, which may include the ATG initiationcodon and adjacent sequences, can be of a variety of origins, bothnatural and synthetic.

The AAV genome of the inventive parvovirus vectors may optionallyinclude the genes that encode the AAV Cap and Rep proteins. In preferredembodiments, the genes encoding at least one of the AAV Cap proteins orat least one of the AAV Rep proteins will be deleted from the rAAVgenome. According to this embodiment, the Cap and Rep functions may beprovided in trans, e.g., from a transcomplementing packaging vector orby a stably-transformed packaging cell line. In more preferredembodiments, the genes encoding all of the AAV Cap proteins or all ofthe AAV Rep proteins will be deleted from the rAAV genome. Finally, inthe most preferred embodiments, all of the AAV cap genes and all of theAAV rep genes are deleted from the AAV vector. This configurationmaximizes the size of the heterologous nucleic acid sequence(s) that canbe carried by the AAV genome, simplifies cloning procedures, andminimizes recombination between the rAAV genome and the rep/cappackaging sequences provided in trans.

In hybrid parvoviruses according to the present invention, theparvovirus cap genes (if present) may encode the Cap proteins from anyparvovirus, preferably an AAV. In contrast, the rep genes (if present)will typically and preferably be AAV rep genes. It is further preferredthat the rep genes and the AAV inverted terminal repeat(s) carried bythe AAV genome are of the same serotype. Moreover, if the cap genes areAAV cap genes, the rep genes will preferably be of a different AAVserotype from the AAV cap genes.

The rep genes/proteins of different AAV serotypes may be evaluated forthose giving the highest titer vector in connection with particularhybrid parvoviruses without undue experimentation. In particularpreferred embodiments, the AAV rep genes encode a temperature-sensitiveRep78 and/or Rep68 protein as described by Gavin et al., (1999) J.Virology 73:9433 (the disclosure of which is incorporated herein byreference in its entirety).

As described above, the Cap proteins of the hybrid parvovirus aredifferent from the AAV genome (i.e., the Cap proteins are either from adifferent AAV serotype or from an autonomous parvovirus). In addition,as described above, the Cap proteins will typically and preferably bedifferent from the rep genes (if present).

Accordingly, in particular preferred embodiments, the hybrid parvovirushas an AAV type 3, 4 or 5 capsid and carries an AAV type 2 genomeincluding an AAV type 2 ITR(s). The AAV genome may additionally includethe AAV rep genes (preferably type 2) and AAV cap genes (preferably, AAVtype 3, 4, or 5, respectively). Typically, however, the AAV genome willbe a rAAV genome, and the rep and cap genes will be deleted therefrom.In an alternate preferred embodiment, the hybrid parvovirus has a B19capsid and carries an AAV genome, more preferably an AAV type 2 genome,including an AAV ITR(s). The AAV genome may optionally encode the AAVRep proteins (preferably AAV type 2) and B19 capsid proteins, butpreferably is a rAAV genome lacking these sequences.

The present invention also provides nucleotide sequences and vectors(including cloning and packaging vectors) encoding the inventive AAVgenomes and the parvovirus cap gene(s) and the AAV rep gene(s) forproducing the inventive hybrid parvoviruses. As described above, inpreferred embodiments, at least one of the AAV rep genes or one of theAAV cap genes, more preferably all of the AAV rep genes and the AAV capgenes, are deleted from the AAV genome. The Rep and Cap functions may beprovided in trans by packaging vector(s). Multiple packaging vectors(e.g., two, three, etc.) may be employed, but typically and preferablyall of the Rep and Cap functions are provided by a single packagingvector.

Cloning and packaging vectors may be any vector known in the art.Illustrative vectors include, but are not limited to, plasmids, nakedDNA vectors, bacterial artificial chromosomes (BACs), yeast artificialchromosomes (YACs), and viral vectors. Preferred viral vectors includeAAV, adenovirus, herpesvirus, Epstein-Barr virus (EBV), baculovirus, andretroviral (e.g., lentiviral) vectors, more preferably, adenovirus andherpesvirus vectors.

The present invention also provides cells containing the inventivevectors. The cell may be any cell known in the art including bacterial,protozoan, yeast, fungus, plant, and animal (e.g., insect, avian,mammalian) cells.

Further provided are stably-transformed packaging cells that express thesequences encoding the parvovirus cap gene(s) and/or the AAV rep gene(s)for producing the inventive hybrid parvoviruses. Any suitable cell knownin the art may be employed to express the parvovirus cap and/or repgene(s). Mammalian cells are preferred (e.g., HeLa cells). Alsopreferred are trans-complementing packaging cell lines that will providefunctions deleted from a replication-defective helper virus, e.g., 293cells or other E1a trans-complementing cells.

In particular preferred embodiments, at least one of the rep genes or atleast one of the cap genes, more preferably all of the cap genes or allof the rep genes are stably integrated into the genetic material of thepackaging cell and are expressed therefrom. Typically, and mostpreferably, all of the parvovirus cap genes and all of the AAV rep genesare stably integrated and expressed by the packaging cell.

The cap and rep genes and proteins are as described above with respectto hybrid AAV genomes. Thus, the packaging vector(s) and/or packagingcell may encode the cap genes from any parvovirus. Preferred are theB19, AAV type 3, AAV type 4 and AAV type 5 cap genes. Likewise, thepackaging vector(s) and/or packaging cell may encode the rep genes fromany parvovirus. Preferably, however, the rep genes will be AAV genes,more preferably, AAV type 2, AAV type 3, AAV type 4, or AAV type 5 repgenes. Most preferably, the rep genes are AAV type 2 rep genes. Inparticular preferred embodiments, the AAV rep sequences encode atemperature-sensitive Rep78 or Rep68 protein as described by Gavin etal., (1999) J. Virology 73:9433.

The expression of the cap and rep genes, whether carried by the rAAVgenome, a packaging vector, or stably integrated into the genome of apackaging cell may be driven by any promoter or enhancer element knownin the art, as described in more detail above. Preferably, the cap orrep genes (more preferably both) are operably associated with parvoviruspromoters. In the most preferred embodiments, the cap genes and repgenes are operably associated with their authentic promoters (i.e., thenative promoter).

A previous report indicates that expression of parvovirus cap genes froma B19/AAV type 2 hybrid helper vector cannot be achieved using authenticpromoters. Ponnazhagan et al., (1998) J. Virology 72:5224, attempted togenerate a helper vector for producing a B19 parvovirus capsid packagingan AAV type 2 genome. These investigators reported that virus could notbe packaged when the cap genes on the helper vector were driven byeither the authentic AAV p40 or B19 p6 promoters. Packaging of virus wasonly successfully achieved when the CMV promoter (a strong promoter) wassubstituted for the authentic promoters. It appears that the naturalregulation of the cap genes was disrupted, and cap gene expression wasrestored only by splitting up the rep and cap coding regions and usingan exogenous promoter to drive cap gene expression.

Likewise, the cloning strategy proposed by U.S. Pat. No. 5,681,731 toLebkowski et al. for generating hybrid viruses comprising an autonomousparvovirus capsid encapsidating a rAAV genome (col. 15-16) will fail toresult in packaged virus.

In contrast, the present invention provides hybrid packaging vectors andpackaging cells in which parvovirus promoters, preferably the authenticpromoters, may be used to drive expression of the parvovirus cap and repgenes to produce the inventive hybrid parvoviruses. Previous efforts tocreate hybrid parvovirus cap/rep gene constructs using authenticpromoters have not succeeded, at least in part, because theseinvestigators failed to preserve the integrity of the splice sitesrequired for proper processing of the rep genes. The presentinvestigations have utilized a seamless cloning strategy (StratageneUSA) in which the splice sites within the rep genes have been preserved.Alternatively, site-directed mutagenesis (or similar techniques) may beused to restore the splice sites to the hybrid virus constructs.

The present invention further encompasses methods of producing theinventive hybrid parvoviruses. Hybrid parvovirus particles according tothe invention may be produced by introducing an AAV genome to bereplicated and packaged into a permissive or packaging cell, as thoseterms are understood in the art (e.g., a “permissive” cell can beinfected or transduced by the virus; a “packaging” cell is a stablytransformed cell providing helper functions). Preferably, the AAV genomeis a rAAV genome encoding a heterologous nucleic acid sequence(s) thatis flanked by at least one AAV ITR. rAAV genomes, AAV ITRs, andheterologous nucleic acid sequences are all as described in more detailhereinabove. The AAV genome may be provided to the cell by any suitablevector, as described hereinabove.

Any method of introducing the vector carrying the AAV genome into thepermissive cell may be employed, including but not limited to,electroporation, calcium phosphate precipitation, microinjection,cationic or anionic liposomes, and liposomes in combination with anuclear localization signal. In embodiments wherein the AAV genome isprovided by a virus vector, standard methods for producing viralinfection may be used.

Any suitable permissive or packaging cell known in the art may beemployed to produce AAV vectors. Mammalian cells are preferred. Alsopreferred are trans-complementing packaging cell lines that providefunctions deleted from a replication-defective helper virus, e.g., 293cells or other E1a trans-complementing cells.

The AAV genome may contain some or all of the AAV cap and rep genes, asdescribed herein. Preferably, however, some or all of the cap and repfunctions are provided in trans by introducing a packaging vector(s), asdescribed above, into the cell. Alternatively, the cell is a packagingcell that is stably transformed to express the cap and/or rep genes.Packaging vectors and packaging cells are as described hereinabove.

In addition, helper virus functions are provided for the AAV vector topropagate new virus particles. Both adenovirus and herpes simplex virusmay serve as helper viruses for AAV. See, e.g., BERNARD N. FIELDS etal., VIROLOGY, volume 2, chapter 69 (3d ed., Lippincoft-RavenPublishers). Exemplary helper viruses include, but are not limited to,Herpes simplex (HSV) varicella zoster, cytomegalovirus, and Epstein-Barrvirus. The multiplicity of infection (MOI) and the duration of theinfection will depend on the type of virus used and the packaging cellline employed. Any suitable helper vector may be employed. Preferably,the helper vector(s) is a plasmid, for example, as described by Xiao etal, (1998) J. Virology 72:2224. The vector can be introduced into thepackaging cell by any suitable method known in the art, as describedabove.

AAV vectors can be produced by any suitable method known in the art. Thetraditional production of rAAV vectors entails co-transfection of arep/cap vector encoding AAV helper and the AAV vector into human cellsinfected with adenovirus (Samulski et al., (1989) J. Virology 63:3822).Under optimized conditions, this procedure can yield up to 10⁹infectious units of rAAV per ml. One drawback of this method, however,is that it results in the co-production of contaminating wild-typeadenovirus in rAAV preparations. Since several adenovirus proteins(e.g., fiber, hexon, etc.) are known to produce a cytotoxic T-lymphocyte(CTL) immune response in humans (Yang and Wilson, (1995) J. Immunol.155:2564; Yang et al., (1995) J. Virology 69:2004; Yang et al., (1994)Proc. Nat. Acad. Sci. USA 91:4407), this represents a significantdrawback when using these rAAV preparations (Monahan et al., (1998) GeneTherapy 5:40).

AAV vector stocks free of contaminating helper virus may be obtained byany method known in the art. For example, AAV and helper virus may bereadily differentiated based on size. AAV may also be separated awayfrom helper virus based on affinity for a heparin substrate (Zolotukhinet al. (1999) Gene Therapy 6:973). Preferably, deletedreplication-defective helper viruses are used so that any contaminatinghelper virus is not replication competent. As a further alternative, anadenovirus helper lacking late gene expression may be employed, as onlyadenovirus early gene expression is required to mediate packaging of AAVvirus. Adenovirus mutants defective for late gene expression are knownin the art (e.g., ts100K and ts149 adenovirus mutants).

A preferred method for providing helper functions through infectiousadenovirus employs a non-infectious adenovirus miniplasmid that carriesall of the helper genes required for efficient AAV production (Ferrariet al., (1997) Nature Med. 3:1295; Xiao et al., (1998) J. Virology72:2224). The rAAV titers obtained with adenovirus miniplasmids areforty-fold higher than those obtained with conventional methods ofwild-type adenovirus infection (Xiao et al., (1998) J. Virology72:2224). This approach obviates the need to perform co-transfectionswith adenovirus (Holscher et al, (1994), J. Virology 68:7169; Clark etal., (1995) Hum. Gene Ther. 6:1329; Trempe and Yang, (1993), in, FifthParvovirus Workshop, Crystal River, Fla.).

Other methods of producing rAAV stocks have been described, includingbut not limited to, methods that split the rep and cap genes ontoseparate expression cassettes to prevent the generation ofreplication-competent AAV (see, e.g., Allen et al, (1997) J. Virol.71:6816), methods employing packaging cell lines (see, e.g., Gao et al,(1998) Human Gene Therapy 9:2353; Inoue et al., (1998) J. Virol.72:7024), and other helper virus free systems (see, e.g., U.S. Pat. No.5,945,335 to Colosi).

Accordingly, the AAV genome to be packaged, parvovirus cap genes, AAVrep genes, and helper functions are provided to a cell (e.g., apermissive or packaging cell) to produce AAV particles carrying the AAVgenome. The combined expression of the rep and cap genes encoded by theAAV genome and/or the packaging vector(s) and/or the stably transformedpackaging cell results in the production of a hybrid parvovirus in whicha parvovirus capsid encapsidates an AAV genome. The hybrid parvovirusparticles are allowed to assemble within the cell, and are thenrecovered by any method known by those of skill in the art.

The reagents and methods disclosed herein may be employed to producehigh-titer stocks of the inventive parvovirus vectors. Preferably, theparvovirus stock has a titer of at least about 10⁵ transducing units(tu)/ml, more preferably at least about 10⁶ tu/ml, more preferably atleast about 10⁷ tu/ml, yet more preferably at least about 10⁸ tu/ml, yetmore preferably at least about 10⁹ tu/ml, still yet more preferably atleast about 10¹⁰ tu/ml, still more preferably at least about 10¹¹ tu/ml,or more.

Alternatively stated, the parvovirus stock preferably has a titer of atleast about 1 tu/cell, more preferably at least about 5 tu/cell, stillmore preferably at least about 20 tu/cell, yet more preferably at leastabout 50 tu/cell, still more preferably at least about 100 tu/cell, morepreferably still at least about 250 tu/cell, most preferably at leastabout 500 tu/cell, or even more.

It is also preferred that the parvovirus is produced at essentiallywild-type titers.

Those skilled in the art will appreciate that the instant invention alsoencompasses hybrid parvovirus vectors that contain chimeric capsidsand/or capsids that have been modified by insertion of an amino acidsequence(s) into the capsid to confer altered tropisms or othercharacteristics, each as discussed in more detail below. The viruscapsids may also include other modifications, e.g., deletion, insertion,point and/or missense mutations, and the like.

Those skilled in the art will further appreciate that mutations mayincidentally be introduced into the cap and/or rep genes as a result ofthe particular cloning strategy employed. For example, the constructionof sequences encoding hybrid parvovirus genomes as described above mayresult in chimeric rep genes (and proteins) because of the overlap ofthe rep and cap sequences (e.g., the cap genes and 3′ end of the repgenes may be AAV type 3, and the remainder of the rep genes may be AAVtype 2). As described above, chimeric AAV rep genes in which the 3′region is derived from an autonomous parvovirus will generally notfunction as the splicing signals are not conserved among AAV and theautonomous parvoviruses, unless site-directed mutagenesis, or a similartechnique, is employed to restore the splice sites to the hybrid virusconstructs.

II. Chimeric Viruses.

The present invention further provides the discovery that chimericparvoviruses may be constructed that possess unique capsid structuresand characteristics. The strategy described above focused on alteringAAV virus structure and function by cross-packaging AAV genomes withindifferent parvovirus capsids. Further diversity in virus particles maybe achieved by substituting a portion of the parvovirus capsid with aportion of a capsid(s) from a different (i.e., another or foreign)parvovirus(es). Alternatively, a portion of a different parvoviruscapsid(s) may be inserted (i.e., rather than substituted) into theparvovirus capsid to create a chimeric parvovirus capsid. Also disclosedare vectors, packaging cells, and methods for constructing chimericparvovirus particles. The chimeric parvoviruses disclosed herein maypossess new antigenic properties, packaging capabilities, and/orcellular tropisms. The chimeric capsids and virus particles of theinvention are also useful for raising chimera-specific antibodiesagainst the novel capsid structures.

Parvoviruses, AAV, and rAAV genomes are as described above with respectto hybrid parvoviruses.

As used herein, a “chimeric” parvovirus is a parvovirus in which aforeign (i.e., exogenous) capsid region(s) from a differentparvovirus(s) is inserted or substituted into the parvovirus capsid.Preferably the foreign capsid region is substituted for one of thenative parvovirus capsid regions. In particular embodiments, the foreigncapsid region is swapped for the homologous capsid region within theparvovirus capsid. It is also preferred that the parvovirus capsid is anAAV capsid. According to this embodiment, the AAV capsid may be of anyAAV serotype (e.g., type 1, type 2, type 3, type 4, type 5, type 6,etc., as described above). More preferably, the AAV capsid is an AAVtype 2, type 3, type 4, or type 5 capsid, most preferably an AAV type 2capsid.

Those skilled in the art will appreciate that the chimeric parvovirusmay additionally be a hybrid parvovirus (as described above) or may be atargeted, or otherwise modified, parvovirus (as described below). Thoseskilled in the art will further appreciate that due to the overlap inthe sequences encoding the parvovirus capsid proteins, a singleinsertion or substitution may affect more than one capsid subunit.

The foreign parvovirus capsid region may be from any parvovirus (i.e.,an autonomous parvovirus or dependovirus) as described above.Preferably, the foreign capsid region is from the human B19 parvovirusor from AAV type 3, type 4, or type 5.

The foreign parvovirus capsid region may constitute all or substantiallyall of a capsid subunit(s) (i.e., domain, for example the Vp1, Vp2 andVp3 subunits of AAV or the Vp1 and Vp2 subunits of B19 virus) or aportion of a capsid subunit. Conversely, more than one foreign capsidsubunit may be inserted or substituted into the parvovirus capsid.Likewise, a portion of a parvovirus capsid subunit or one or moreparvovirus capsid subunits may be replaced with one or more foreigncapsid subunits, or a portion thereof. Furthermore, the chimericparvovirus capsid may contain insertions and/or substitutions at morethan one site within the capsid. According to this embodiment, themultiple insertions/substitutions may be derived from more than oneparvovirus (e.g., two, three, four, five or more). Generally, it ispreferred that at least one subunit from the parvovirus capsid isretained in the chimeric capsid, although this is not required.

In particular embodiments of the invention, the foreign parvoviruscapsid region that is inserted or substituted into the native parvoviruscapsid is at least about 2, 5, 10, 12, 15, 20, 30, 50, or 100 aminoacids in length.

The inventive chimeric parvoviruses may contain any parvovirus genome,preferably an AAV genome, more preferably a recombinant AAV genome.Embodiments wherein the AAV genome is packaged within a chimeric AAVcapsid of the same serotype is also preferred. AAV type 2 genomes aremost preferred regardless of the composition of the chimeric parvoviruscapsid.

In preferred embodiments of the invention, the chimeric parvoviruscomprises an AAV capsid, more preferably an AAV type 2 capsid, in whicha capsid region from a B19 parvovirus has been substituted for one ofthe AAV capsid domains. In other preferred embodiments, the chimericparvovirus comprises an AAV capsid (more preferably, an AAV type 2capsid) in which the Vp3 subunit of the AAV capsid has been replaced bythe B19 Vp2 subunit.

In alternative preferred embodiments, the chimeric parvovirus comprisesan AAV capsid (preferably type 2) in which the Vp1 and Vp2 subunits arereplaced by the Vp1 subunit of a B19 parvovirus.

In other preferred embodiments, the chimeric parvovirus comprises an AAVtype 2 capsid in which the type 2 Vp1 subunit has been replaced by theVp1 subunit from an AAV type 1, 3, 4, 5, or 6 capsid, preferably a type3, 4, or 5 capsid. Alternatively, the chimeric parvovirus has an AAVtype 2 capsid in which the type 2 Vp2 subunit has been replaced by theVp2 subunit from an AAV type 1, 3, 4, 5, or 6 capsid, preferably a type3, 4, or 5 capsid. Likewise, chimeric parvoviruses in which the Vp3subunit from an AAV type 1, 3, 4, 5 or 6 (more preferably, type 3, 4 or5) is substituted for the Vp3 subunit of an AAV type 2 capsid arepreferred. As a further alternative, chimeric parvoviruses in which twoof the AAV type 2 subunits are replaced by the subunits from an AAV of adifferent serotype (e.g., AAV type 1, 3, 4, 5 or 6) are preferred. Inexemplary chimeric parvoviruses according to this embodiment, the Vp1and Vp2, or Vp1 and Vp3, or Vp2 and Vp3 subunits of an AAV type 2 capsidare replaced by the corresponding subunits of an AAV of a differentserotype (e.g., AAV type 1, 3, 4, 5 or 6). Likewise, in other preferredembodiments, the chimeric parvovirus has an AAV type 1, 3, 4, 5 or 6capsid (preferably the type 2, 3 or 5 capsid) in which one or twosubunits have been replaced with those from an AAV of a differentserotype, as described above for AAV type 2.

In still other preferred embodiments, the minor subunit of oneparvovirus may be substituted with any minor subunit of anotherparvovirus (e.g., Vp2 of AAV type 2 may be replaced with Vp1 from AAVtype 3; Vp1 of B19 may substitute for Vp1 and/or VP2 of AAV). Likewise,the major capsid subunit of one parvovirus may be replaced with themajor capsid subunit of another parvovirus.

The nucleotide sequences encoding specific chimeric capsids include thesequence given as nucleotides 2133 to 4315 of SEQ ID NO:2. This sequencecontains the AAV2 rep coding sequences, most of the AAV2 Vp1 and Vp3coding sequences, and the entire AAV4 Vp2 coding sequences and some ofthe AAV4 Vp1 and Vp3 coding sequences in a pBluescript backbone.Preferably, the chimeric parvoviruses having the capsid encoded by thehelper given in SEQ ID NO:2 carry an AAV2 genome.

Alternatively, the nucleotide sequence of the chimeric capsid issubstantially homologous to the capsid coding sequence given asnucleotides 2133 to 4315 of SEQ ID HO:2, As a further alternative, thenucleotide squence of the chimeric capsid encodes the same amino acidsequence as nucleotides 2133 to 4315 of SEQ ID NO:2. The term“substantially homologous” is as defined hereinbelow.

The present invention also provides the discovery that chimericparvoviruses may generate unique capsid structures that do not resemblethe constituent parvovirus capsids. For example, the presentinvestigations have discovered that B19/AAV type 2 chimeras, in whichthe Vp3 subunit of AAV type 2 has been replaced by the Vp2 subunit of ahuman B19 virus, results in the expected 23-28 nm particle (typical forwt AAV) and a novel 33-38 nm particle. The larger particles were presentat the same density as the 23-28 nm particles in a cesium isopycnicgradient.

While not wishing to be held to any particular theory of the invention,these results suggest that this particle is formed by changing thetriangulation number from T=1 to T=3, to yield a larger particlecontaining 180 copies of the major capsid component instead of 60. Thisnovel particle may package larger than wild-type genomes due to itsincreased size. In particular preferred embodiments, the B19/AAV type 2chimeric parvovirus capsid (B19 Vp2 swapped for AAV2 Vp3) has the aminoacid sequence given as SEQ ID NO:4.

The present invention further provides B19/AAV chimeric capsids andparvoviruses having larger than wild-type capsid structures (e.g.,larger than about 28 nm, 30 nm, 32 nm, 34 nm, 36 nm, 38 nm, 40 nm ormore in diameter). Alternatively stated, the present invention providesB19/AAV chimeric capsids and parvoviruses with capsid structurescontaining more than the wild-type number of capsid subunits (e.g.,greater than about 60 capsid subunits, greater than about 90 capsidsubunits, greater than about 120 capsid subunits, greater than about 180capsid subunits). As a further alternative statement, the presentinvention provides B19/AAV capsids and parvoviruses that efficientlypackage greater than wild-type genomes (e.g., greater than about 4.8 kb,5.0 kb, 5.2 kb, 5.4 kb, 5.6 kb, 5.8 kb, 6.0 kb, 6.2 kb, 6.4 kb, 6.6 kb,6.8 kb or more). Preferably, the larger genomes are efficiently packagedto produce viral stocks having the titers described hereinabove.

It is also preferred that the B19/AAV chimeras have altered antigenicproperties. In particular, it is preferred that the B19/AAV chimeras maybe administered to a subject that has antibodies against the serotype ofthe AAV without immune clearance, i.e., the chimera is not recognized bythe AAV serotype-specific antibodies.

In other preferred embodiment of the invention, the nucleotide sequenceof the B19/AAV chimeric capsid is substantially homologous to thesequence given as SEQ ID NO:3 and encodes a chimeric parvovirus capsid.This definition is intended to include AAV of other serotypes andnon-human B19 viruses. As used herein, sequences that are “substantiallyhomologous” are at least 75%, and more preferably are 80%, 85%, 90%,95%, or even 99% homologous or more.

High stringency hybridization conditions that permit homologousnucleotide sequences to hybridize are well known in the art. Forexample, hybridization of homologous nucleotide sequences to hybridizeto the sequence given SEQ ID NO:3 may be carried out in 25% formamide,5×SSC, 5× Denhardt's solution, with 100 μg/ml of single stranded DNA and5% dextran sulfate at 42° C., with wash conditions of 25% formamide,5×SSC, 0.1% SDS at 42° C. for 15 minutes, to allow hybridization ofsequences of about 60% homology. More stringent conditions arerepresented by a wash stringency of 0.3M NaCl, 0.03 M sodium citrate,0.1% SDS at 600 or even 70° C. using a standard in situ hybridizationassay. (See SAMBROOK ET AL., MOLECULAR CLONING, A LABORATORY MANUAL (2ded. 1989)).

In other preferred embodiments, the chimeric B19/AAV capsid has theamino acid sequence encoded by the sequence given in SEQ ID NO:3 (SEQ IDNO:4).

In other particular preferred embodiments, a non-conserved region(s) ofa parvovirus capsid is inserted or substituted, preferably substituted,into another parvovirus capsid. Preferably a non-conserved region(s) issubstituted for the same (i.e., homologous) region from a differentparvovirus. Parvovirus specific (including AAV serotype specific)characteristics are likely associated with such non-conserved regions.It is also likely that non-conserved regions can best toleratealterations. In particular embodiments, the looped-out regions of theparvovirus major capsid subunits are swapped between two parvoviruses,more preferably an AAV and a parvovirus, still more preferably betweentwo AAV of different serotypes.

With particular respect to AAV type 2, although the crystal structure ofthis virus has not been solved, structural correlations have been madebased on sequence information. The structural correlations suggest thatthe Vp3 subunit of AAV type 2 has eight β-barrel motifs, and that thesemotifs are separated by looped out regions (Chapman et al., Virology194:419). Recently, the sequence of AAV type 3 has been determined byMuramatsu et al., (1996) Virology 221:208. The amino acid homologybetween Vp3 of AAV type 2 and AAV type 3 is 89%, with the region definedas loop 3/4 having 70% homology (Id.). Additionally, AAV type 3 does notbind to the same receptor as AAV type 2 (Mizukami et al., Virology217:124). The divergent amino acid sequences in loops 3 and 4 mayexplain the differences in cellular receptors used by AAV type 2 and AAVtype 3, and the resulting disparities in cellular tropism. Accordingly,in preferred embodiments of the instant invention, chimeric AAVparticles are constructed in which loop 3/4, or a portion thereof, ofAAV type 2 is swapped for the AAV type 3 loop 3/4, or vice versa.

In other embodiments, the chimeric parvovirus comprises an AAV type 2capsid in which loop 1, 2, 3, and/or 4 of the Vp3 subunit have beenreplaced by the corresponding loop region(s) of an AAV of a differentserotype (e.g., type 1, 3, 4, 5 or 6). In illustrative embodiments, theloop 24 region of the AAV type 2 Vp3 subunit is replaced by the loop 2-4region of a type 3 or type 4 virus.

Likewise, in other preferred embodiments, the chimeric parvoviruscomprises an AAV type 1, 3, 4, 5 or 6 capsid in which the loop 1, 2, 3and/or 4 region of the Vp3 subunit is replaced by the correspondingregion of a different AAV serotype. Exemplary embodiments include, butare not limited to, a chimeric parvovirus comprising an AAV type 3 ortype 4 capsid in which the loop 2-4 region of the Vp3 subunit isreplaced by the AAV type 2 loop 2-4 region.

The present invention further provides chimeric parvoviruses comprisingan AAV capsid in which a loop region(s) in the major Vp3 subunit isreplaced by a loop region (s) (preferably, a corresponding loopregion(s)) from the major subunit of an autonomous parvovirus. Inparticular, the loop region 1, 2, 3 and/or 4 from an AAV type 1, 2, 3,4, 5, or 6 Vp3 subunit is replaced with a loop region from the majorsubunit of an autonomous parvovirus.

The nucleotide sequences encoding specific chimeric capsids include thesequence given as nucleotides 2133 to 4342 of SEQ ID NO:5. This sequencecontains the AAV2 rep coding sequences, most of the AAV2 capsid codingsequences, with the exception that loops 2-4 from the AAV2 Vp3 subunitwere replaced with the corresponding region from AAV3, in a pBluescriptbackbone.

Alternatively, the nucleotide sequence of the chimeric capsid issubstantially homologous to the sequence given as nucleotides 2133 to4342 of SEQ ID NO:5. As a further alternative, the nucleotide sequenceof the chimeric capsid has the same amino acid sequence as the capsidencoded by nucleotides 2133 to 4342 of SEQ ID NO:5. The term“substantially homologous” is as defined hereinabove.

Chimeric parvoviruses may be constructed as taught herein or by otherstandard methods known in the art. Likewise, those skilled in the artmay evaluate the chimeric parvoviruses thus generated for assembly,packaging, cellular tropism, and the like, as described herein or byother standard methods known in the art, without undue experimentation.

Another aspect of the present invention is a chimeric parvovirus capsidprotein (preferably an AAV Vp1, Vp2 or Vp3 capsid protein) with at leastone capsid region from another parvovirus(es) inserted or substitutedtherein (preferably, substituted). The introduction of the foreigncapsid protein into a parvovirus capsid provides altered characteristics(e.g., immunogenic, tropism, etc.) to a virus capsid or particle(preferably a parvovirus capsid or particle) incorporating the chimericparvovirus capsid protein. Alternatively, the chimeric parvovirus capsidprotein may facilitate detection or purification of a virus capsid orparticle (preferably parvovirus capsid or particle) incorporating thechimeric parvovirus capsid protein. In particular preferred embodiments,the antigenic properties of an AAV capsid or particle of a particularserotype may be altered (e.g., changed or modified) or diminished (e.g.,reduced or mitigated) by incorporation of the chimeric parvovirus capsidregion for the native capsid region. According to this embodiment,chimeric capsid proteins may be used to obviate or reduce immuneclearance in subjects that have immunity against the serotype of the AAVcapsid or particle (e.g., to permit multiple virus administrations).Changes or reductions in antigenic properties may be assessed, e.g., incomparison to an AAV capsid or particle that is identical except for thepresence of the chimeric parvovirus capsid protein.

The present invention also encompasses empty chimeric parvovirus capsidstructures. Empty capsids may be used for presentation or delivery ofpeptides or proteins (e.g., antigens to produce an immune response),nucleic acids, or other compounds (see, e.g., Miyamura et al., (1994)Proc. Nat. Acad. Sci USA 91:8507; U.S. Pat. No. 5,916,563 to Young etal., U.S. Pat. No. 5,905,040 to Mazzara et al, U.S. Pat. No. 5,882,652,U.S. Pat. No. 5,863,541 to Samulski et al.; the disclosures of which areincorporated herein in their entirety by reference). Empty capsids maybe produced by any method known in the art. (see, e.g., id.).

The chimeric parvoviruses and capsids of the invention further find usein raising antibodies against the novel capsid structures. Antibodiesmay be produced by methods that are known to those skilled in the art.

The present invention also provides cloning vectors, transcomplementingpackaging vectors, packaging cells, and methods for producing theinventive chimeric parvovirus particles disclosed herein. In general,vectors, packaging cells, and methods for producing chimericparvoviruses are as described above with respect to hybrid parvoviruses.In addition, at least one of the cap genes (encoded by the rAAV genome,a packaging vector(s), or the packaging cell) has inserted therein atleast one nucleic acid sequence encoding a foreign amino acid sequencefrom a non-homologous parvovirus (as described above).

III. Targeted Parvoviruses.

A further aspect of the present invention are parvovirus vectorscomprising a parvovirus capsid and a recombinant AAV genome, wherein anexogenous targeting sequence has been inserted or substituted into theparvovirus capsid. The parvovirus vector is preferably targeted (i.e.,directed to a particular cell type or types) by the substitution orinsertion of the exogenous targeting sequence into the parvoviruscapsid. Alternatively stated, the exogenous targeting sequencepreferably confers an altered tropism upon the parvovirus. As yet afurther alternative statement, the targeting sequence increases theefficiency of delivery of the targeted vector to a cell.

As is described in more detail below, the exogenous targeting sequencemay be a virus capsid sequence (e.g., an autonomous parvovirus capsidsequence, AAV capsid sequence, or any other viral capsid sequence) thatdirects infection of the parvovirus to a particular cell type(s). As analternative, the exogenous amino acid sequence may encode any peptide orprotein that directs entry of the parvovirus vectors into a cell(s). Inpreferred embodiments, the parvovirus capsid is an AAV capsid, morepreferably, an AAV type 2 capsid.

An “altered” tropism, as used herein, includes reductions orenhancements in infectivity with respect to a particular cell type(s) ascompared with the native parvovirus lacking the targeting sequence(s).An “altered” tropism also encompasses the creation of a new tropism(i.e., the parvovirus would not infect a particular cell type(s) to asignificant or, alternatively, a detectable extent in the absence of theexogenous amino acid sequence). Alternatively, an “altered tropism” mayrefer to a more directed targeting of the parvovirus vector to aparticular cell type(s) as compared with the native parvovirus, but thetarget cells may typically be infected by the native parvovirus as well(e.g., a narrowed tropism). As a further alternative, an “altered”tropism refers to a more efficient delivery of a targeted parvovirus ascompared with the native parvovirus (e.g., a reduced Multiplicity ofInfection, “MOI”).

The term “reduction in infectivity”, as used herein, is intended toencompass both an abolishment of the wild-type tropism as well as adiminishment in the wild-type tropism or infectivity toward a particularcell type(s). The diminished infectivity may be a 25%, 50%, 75%, 90%,95%, 99%, or more decrease in infectivity with respect to the wild-typelevel of infectivity. By “enhancement in infectivity”, it is meant thatthe infectivity with respect to a particular cell type(s) is increasedabove that observed with the wild-type parvovirus, e.g., by at least25%, 50%, 75%, 100%, 150%, 200%, 300%, or 500%, or more.

The exogenous targeting sequence(s) may replace or substitute part orall of a capsid subunit, alternatively, more than one capsid subunit. Asa further alternative, more than one exogenous targeting sequence (e.g.,two, three, four, five or more sequences) may be introduced into theparvovirus capsid. In alternative embodiments, insertions andsubstitutions within the minor capsid subunits (e.g., Vp1 and Vp2 ofAAV) are preferred. For AAV capsids, insertions or substitutions in Vp2or Vp3 are also preferred.

Those skilled in the art will appreciate that due to the overlap in thesequences encoding the parvovirus capsid proteins, a single insertion orsubstitution may affect more than one capsid subunit.

As described above, in particular embodiments, the present inventionprovides chimeric parvovirus particles with unique structures andproperties. The substitution and/or insertion of one or more parvoviruscapsid region(s) for another to create a chimeric parvovirus capsid mayresult in the loss of the wild-type parvovirus tropism and/or thedevelopment of a new tropism associated with the exogenous capsidregion(s). Accordingly, targeted parvoviruses may also be chimericparvoviruses as is described in more detail hereinabove. In particular,targeted chimeric parvoviruses are provided in which a capsid subunit(s)or a loop region(s) from the major capsid subunit has been replaced witha capsid subunit(s) or loop region from another parvovirus.

Accordingly, in particular embodiments of the instant invention,chimeric parvovirus particles are constructed in which the capsiddomains that encode the wild-type parvovirus tropism are swapped withcapsid regions or subunits from a different parvovirus sequence, therebydiminishing or even completely abolishing the wild-type tropism. Theseinfection-negative parvoviruses find use as templates for creatingparvoviruses with targeted tropisms. In this manner, a parvovirus with anew or directed tropism, but lacking the wild-type tropism, may begenerated.

In another preferred embodiment, a parvovirus capsid region that directsthe native or wild-type tropism is swapped with a capsid domain thatdirects the tropism of another parvovirus, thereby diminishing orablating the native tropism and concurrently conferring a new tropism tothe chimeric parvovirus. In other embodiments, the foreign capsid regionis substituted or inserted into the parvovirus capsid without reducingor extinguishing the wild-type tropism. As a further alternative, morethan one foreign parvovirus capsid region (e.g., two, three, four, five,or more) is swapped into the parvovirus capsid. For example, a firstforeign capsid region may replace the native capsid region directing thewild-type tropism. Additional foreign capsid regions provide thechimeric capsid with a new tropism(s).

Heparan sulfate (HS) has recently been identified as a primary receptorfor AAV (Summerford and Samulski, (1998) J. Virology 72:1438). Thus, thecapsid structure may be modified to facilitate or enhance binding of AAVto the cellular receptor or to inhibit or prevent binding thereto. Toillustrate, the tropism of the AAV may be altered by swapping out the HSbinding domain for the AAV capsid, for example, with sequences fromother parvoviruses that do contain this HS binding domain or any othersequences.

Several consensus sequences have been identified among ligands that bindto HS receptors. In general, HS appears to bind to sequences includingclusters of basic amino acids. Illustrative consensus sequences includebut are not limited to BBXB, BBBXXB, and RX₇FRXKKXXXK, where B is abasic amino acid, and X is any amino acid. Three sequences containingclusters of basic amino acids are present in the first 170 amino acidresidues of the VP1 capsid protein of AAV type 2 as follows: RX₅KKR atamino acids 116 to 124, K₄KKR at amino acids 137 to 144, and KX₆RKR atamino acids 161 to 170 (AAV type 2 sequence and numbering as describedby Srivastava et al, (1983) J. Virology 45:555, as modified by Ruffinget al., (1994) J. Gen. Virology 75:3385, Muzyczka, (1992) Curr. TopicsMicrobiol. Immunol. 158:97, and Cassinotti et al., (1988) Virology167:176). In addition, the consensus sequence (RX₇FRPKRLNFK) is found inthe VP1 capsid subunit of AAV type 2 at amino acids 299 to 315.

It appears that AAV serotypes 4 and 5 do not bind to cellular HSreceptors, or do so with a low efficiency. Accordingly, in particularembodiments, the HS binding domain of AAV serotypes 1, 2, 3, or 6 may bereplaced with the corresponding region of AAV serotype 4 or 5 to reduceor abolish HS binding. Likewise, HS binding may be conferred upon AAVserotype 4 or 5 by inserting or substituting in the HS binding domainfrom AAV 1, 2, 3 or 6.

The HS consensus sequences are marked by an abundance of basic aminoacids. There is a high density of positively charged amino acids withinthe first 170 residues of the AAV type 2 Vp1 Cap protein, includingthree strings of basic amino acids, which may be involved in an ionicinteraction with the cell surface. Accordingly, in one particularembodiment of the invention, the affinity of an AAV capsid for HSreceptors is reduced or eliminated by creating a targeted parvovirus inwhich some or all of the basic sequences are substituted by othersequences, e.g., from another parvovirus that does not contain the HSbinding domain.

Alternatively, the respiratory syncytial virus heparin binding domainmay be inserted or substituted into a virus that does not typically bindHS receptors (e.g., AAV 4, AAV5, B19) to confer heparin binding to theresulting mutant.

B19 infects primary erythroid progenitor cells using globoside as itsreceptor (Brown et al., (1993) Science 262:114). The structure of B19has been determined to 8 Å resolution (Agbandje-McKenna et al., (1994)Virology 203:106). The region of the B19 capsid that binds to globosidehas been mapped between amino acids 399-406 (Chapman et al., (1993)Virology 194:419), a looped out region between β-barrel structures E andF (Chipman et al., (1996) Proc. Nat. Acad. Sci. USA 93:7502).Accordingly, the globoside receptor binding domain of the B19 capsid maybe inserted/substituted into other parvovirus capsids (preferably an AAVcapsid, more preferably, the AAV type 2 capsid) to target the resultingchimeric parvovirus to erythroid cells.

In more preferred embodiments, the exogenous targeting sequence may beany amino acid sequence encoding a peptide or protein, which is insertedor substituted into the parvovirus capsid to alter the tropism of theparvovirus. The native parvovirus tropism may be reduced or abolished byinsertion or substitution of the amino acid sequence. Alternatively, theinsertion or substitution of the exogenous amino acid sequence maytarget the parvovirus to a particular cell type(s). In yet furtherpreferred embodiments, an exogenous targeting sequence is substituted orinserted into the parvovirus capsid to concurrently ablate the wild typetropism and to introduce a new tropism. For example, a targeting peptidemay be inserted directly into a targeting region of the AAV capsid tosimultaneously disrupt the native tropism (e.g., by interfering withbinding to cellular heparan sulfate receptors) and to direct thetargeted AAV vector to particular cells.

Those skilled in the art will appreciate that the native tropism of aparvovirus may be reduced or abolished without substituting or insertingan exogenous targeting sequence directly into those regions of theparvovirus capsid responsible for the receptor binding. Mutants thathave lost the wild-type tropism are useful as templates for the creationof parvoviruses with. novel tropisms as taught herein. It is preferredthat substitutions or insertions that result in the loss of wild-typetropism act at the level of receptor binding and/or entry into the cell.In other words, it is preferred that the altered parvovirus is otherwisecapable of infecting a cell if entry into the cell is provided by othermeans, e.g., by a bispecific antibody, by targeting peptide or proteinas disclosed herein, or by any other means known in the art.

The exogenous targeting sequence may be any amino acid sequence encodinga protein or peptide that alters the tropism of the parvovirus. Inparticular embodiments, the targeting peptide or protein may benaturally occurring or, alternately, completely or partially synthetic.Exemplary peptides and proteins include ligands and other peptides thatbind to cell surface receptors and glycoproteins, such as RGD peptidesequences, bradykinin, hormones, peptide growth factors (e.g., epidermalgrowth factor, nerve growth factor, fibroblast growth factor,platelet-derived growth factor, insulin-like growth factors I and 11,etc.), cytokines, melanocyte stimulating hormone (e.g., α, βor γ),neuropeptides and endorphins, and the like, and fragments thereof thatretain the ability to target cells to their cognate receptors. Otherillustrative peptides and proteins include substance P, keratinocytegrowth factor, neuropeptide Y, gastrin releasing peptide, interleukin 2,hen egg white lysozyme, erythropoietin, gonadoliberin, corticostatin,β-endorphin, leu-enkephalin, rimorphin, α-neo-enkephalin, angiotensin,pneumadin, vasoactive intestinal peptide, neurotensin, motilin, andfragments thereof as described above. As a further alternative, thetargeting peptide or protein may be an antibody or Fab fragment thatrecognizes, e.g., a cell-surface epitope, such as an anti-receptorantibody. As yet a further alternative, the binding domain from a toxin(e.g., tetanus toxin or snake toxins, such as α-bungarotoxin, and thelike) can be used to target the inventive parvovirus vectors toparticular target cells of interest. In a yet further preferredembodiment the parvovirus vectors may be delivered to a cell using a“nonclassical” import/export signal peptide (e.g., fibroblast growthfactor-1 and -2, interleukin 1, HIV-1 Tat protein, herpes virus VP22protein, and the like) as described by Cleves, (1997) Current Biology7:R318. Also encompassed are peptide motifs that direct uptake byspecific cells, e.g., a FVFLP peptide motif triggers uptake by livercells. Phage display techniques, as well as other techniques known inthe art, may be used to identify peptides that recognize, preferablyspecifically, any cell type of interest.

The term “antibody” as used herein refers to all types ofimmunoglobulins, including IgG, IgM, IgA, IgD, and IgE. The antibodiesmay be monoclonal or polyclonal and may be of any species of origin,including (for example) mouse, rat, rabbit, horse, or human, or may bechimeric antibodies. Also encompassed by the term “antibody” arebispecific or “bridging” antibodies as known by those skilled in theart.

Antibody fragments within the scope of the present invention include,for example, Fab, F(ab′)2, and Fc fragments, and the correspondingfragments obtained from antibodies other than IgG. Such fragments may beproduced by known techniques.

The targeting sequence may alternatively encode any peptide or proteinthat targets the parvovirus particle to a cell surface binding site,including receptors (e.g., protein, carbohydrate, glycoprotein orproteoglycan), as well as any oppositely charged molecule (as comparedwith the targeting sequence or the parvovirus capsid), or other moleculewith which the targeting sequence or targeted parvovirus interact tobind to the cell, and thereby promote cell entry. Examples of cellsurface binding sites include, but are not limited to, heparan sulfate,chondroitin sulfate, and other glycosaminoglycans, sialic acid moietiesfound on mucins, glycoproteins, and gangliosides, MHC I glycoproteins,carbohydrate components found on membrane glycoproteins, including,mannose, N-acetyl-galactosamine, N-acetyl-glucosamine, fucose,galactose, and the like.

As yet a further alternative, the targeting sequence may be a peptide orprotein that may be used for chemical coupling (e.g., through amino acidside groups of arginine or lysine residues) to another molecule thatdirects entry of the parvovirus into a cell.

In other embodiments, the exogenous targeting sequence is substituted orinserted into the capsid to disrupt binding to cellular receptors (e.g.,HS receptor) and/or entry into the cell. For example, the exogenousamino acid sequence may be substituted or inserted into the region(s) ofthe AAV capsid that binds to cellular receptors and/or otherwisemediates entry of the virus into the cell. Preferably, the exogenoustargeting sequence is inserted into the capsid region(s) that interactwith cellular HS receptors (as described above). One illustrativeinsertion mutant that forms intact AAV virions yet fails to bind heparinagarose or infect Hela cells is an AAV type 2 mutant generated byinsertion of an amino acid sequence at bp 3761 of the AAV type 2 genome(within the Vp3 cap gene region).

In a further alternative embodiment, the exogenous amino acid sequenceinserted into the parvovirus capsid may be one that facilitatespurification of the parvovirus. According to this aspect of theinvention, it is not necessary that the exogenous amino acid sequencealso alters the tropism of the modified parvovirus. For example, theexogenous amino acid sequence may include a poly-histidine sequence thatis useful for purifying the parvovirus over a nickel column, as is knownto those skilled in the art. Alternatively, the region of the AAV capsidthat interacts with heparin and/or heparan sulfate may be substituted orinserted into a parvovirus capsid so that the parvovirus may be purifiedby binding to heparin, e.g., as described by Zolotukhin et a., (1999)Gene Therapy 6:973, the disclosure of which is incorporated herein inits entirety by reference.

In other embodiments, the amino acid sequence encodes an antigenicpeptide or protein that may be employed to purify the AAV by standardimmunopurification techniques. Alternatively, the amino acid sequencemay encode a receptor ligand or any other peptide or protein that may beused to purify the modified parvovirus by affinity purification or anyother techniques known in the art (e.g., purification techniques basedon differential size, density, charge, or isoelectric point,ion-exchange chromatography, or peptide chromatography).

In yet other embodiments of the invention, an amino acid sequence may beinserted or substituted into a parvovirus particle to facilitatedetection thereof (e.g., with a antibody or any other detection reagent,as is known in the art). For example, the “flag” epitope may be insertedinto the parvovirus capsid and detected using commercially-availableantibodies (Eastman-Kodak, Rochester, N.Y.). Detectable viruses finduse, e.g., for tracing the presence and/or persistence of virus in acell, tissue or subject.

In still a further embodiment, an exogenous amino acid sequence encodingany antigenic protein may be expressed in the modified capsid (e.g., foruse in a vaccine).

As described below and in Table I, the present investigations have usedinsertional mutagenesis of the capsid coding sequence of AAV serotype 2in order to determine positions within the capsid that tolerate peptideinsertions. Viable mutants were identified with insertions throughouteach of the capsid subunits. These insertion mutants find use for anypurpose in which it is desirable to insert a peptide or protein sequenceinto an AAV capsid, e.g., for purifying and/or detecting virus, or forinserting an antigenic peptide or protein into the capsid. Thenucleotide positions indicated in Table 1 (see Examples) are thepositions at which the restriction sites were made, e.g., the newsequences start at the next nucleotide. For example, for an insertionmutant indicated in Table 1 as having an insertion at nucleotide 2285,the new insertion sequence would begin at nucleotide 2286.

It is preferred to insert the exogenous amino acid sequence within theparvovirus minor Cap subunits, e.g., within the AAV Vp1 and Vp2subunits. Alternately, insertions in Vp2 or Vp3 are preferred. Alsopreferred are insertion mutations at nucleotide 2285, 2356, 2364, 2416,2591, 2634, 2690, 2747, 2944, 3317, 3391, 3561, 3595, 3761, 4046, 4047,and/or 4160 within the AAV type 2 cap genes, preferably, to generate anAAV type 2 vector with an altered tropism as described herein (AAV type2 numbering used herein is as described by Srivastava et al., (1983) J.Virology 45:555, as modified by Ruffing et al., (1994) J. Gen. Virology75:3385, Muzyczka, (1992) Curr. Topics Microbiol. Immunol. 158:97, andCassinotti et al., (1988) Virology 167:176).

Insertions at these nucleotide positions for AAV2 will give rise toamino acid insertions following amino acid 28 (nu 2285), 51 (nu 2356),54 (nu 2364), 71 (nu 2416), 130 (nu 2591), 144 (nu 2634), 163 (nu 2690),182 (nu 2747), 247 (nu 2944), 372 (nu 3317), 396. (nu 3391), 452 (nu3561), 464 (nu 3595), 520 (nu 3761), 521 (nu 3766), 615 (nu 4046 and4047), and 653 (nu 4160) within the AAV2 capsid coding region (using thestarting methionine residue for Vp1 as amino acid 1), or thecorresponding regions of AAV of other serotypes as known by thoseskilled in the art. Those skilled in the art will appreciate that due tothe overlap in the AAV capsid coding regions, these insertions may giverise to insertions within more than one of the capsid proteins (Table2). TABLE 2 Insertion Positions in AAV2 Capsid^(1,2) Insertion site Vp1Vp2 Vp3 (nucleotide) (amino acid) (amino acid) (amino acid) 2285  28 — —2356  51 — — 2364  54 — — 2416  71 — — 2591 130 — — 2634 144  7 — 2690163  26 — 2747 182  45 — 2944 247 110  45 3317 372 235 170 3391 396 259194 3561 452 315 250 3595 464 327 262 3753 517 380 315 3761 520 383 3183766 521 384 319 3789 529 392 327 3858 552 415 350 3960 586 449 384 3961586 449 384 3987 595 458 393 4046 615 478 413 4047 615 478 413 4160 653516 451¹The indicated nucleotide or amino acid refers to the nucleotide oramino acid immediately preceding the inserted sequence.²Vp1 start at nucleotide 2203

Alternatively, the exogenous amino acid sequence is inserted at thehomologous sites to those described above in AAV capsids of otherserotypes as known by those skilled in the art (see, e.g., Chiorini etal, (1999) J. Virology 73:1309). The amino acid positions within the AAVcapsid appear to be highly, or even completely, conserved among AAVserotypes. Accordingly, in particular embodiments, the exogenous aminoacid sequence is substituted at the amino acid positions indicated inTable 2 (new sequence starting at the next amino acid) in AAV other thanserotype 2 (e.g., serotype 1, 3, 4, 5 or 6).

As further alternatives, an exogenous amino acid sequence may beinserted into the AAV capsid at the positions described above tofacilitate purification and/or detection of the modified parvovirus orfor the purposes of antigen presentation, as described above.

One particular AAV type 2 mutant is produced by inserting an amino acidsequence at nucleotide position 2634 of the genome (within the Vp2 capgene region; AAV2 numbering as described above). This mutant forms AAVtype 2 virions with normal morphology by electron microscopy analysis inthe absence of detectable expression of the Vp1 and Vp2 subunits.Moreover, this mutant protects the viral genome and retains binding to aheparin-agarose matrix, although it does not demonstrate infectivity inHeLa cells. This mutant is useful for administration to subjects toavoid an immune response against the Vp1 and Vp2 subunits. It furtherfinds use for insertion of large peptides or proteins into the AAVcapsid structure. As one illustrative example, the adenovirus knobprotein is inserted into this mutant to target the virus to theCoxsackie adenovirus receptor (CAR).

Another particular AAV type 2 insertion mutant is produced by insertionof an exogenous amino acid sequence at bp 3761 of the genome (within theVp3 capsid coding region). This mutant protects the viral genome andforms morphologically normal capsid structures, but does not bindheparin-agarose and fails to infect HeLa cells. This mutant isparticularly useful as a reagent for creating AAV vectors lacking thenative tropism. For example, a new targeting region may be introducedinto this mutant at bp 3761 or at another site. As shown in Table 1, thepresent investigations have discovered a variety of positions within theAAV capsid that tolerate insertion of exogenous peptides and retaininfectivity (e.g., at bp 2356, 2591, 2690, 2944, 3595, and/or 4160 ofthe AAV type 2 genome).

In other preferred embodiments, AAV vectors with multiple insertionsand/or substitutions are created to provide AAV vectors exhibiting adesired pattern of infectivity, e.g., a non-infectiousinsertion/substitution mutation and an infectious mutation (e.g., asshown in Table 1) may be combined in a single AAV vector. As oneillustrative example, a peptide insertion may be made at bp 3761 of theAAV type 2 genome (within the Vp3 subunit) to create a non-infectiousheparin binding negative mutant. A second peptide insertion may be madeat bp 2356 (alternatively, bp 2591, 2690, 2944, 3595 or 4160) to targetthe vector. The inserted peptide may be one that directs the AAV type 2vector to target cells of interests. In particular embodiments,bradykinin may be inserted at any of the foregoing sites to target thevector to lung epithelial cells (e.g., for the treatment of cysticfibrosis or other lung disorders) or the adenovirus knob protein may beinserted at the foregoing sites to target the vector to cells expressingCAR receptors. Alternatively, this vector may be employed for antigenpresentation to produce an immune response.

In other embodiments, the substitution or insertion (preferablyinsertion) is made at nucleotides 3789 or 3961 of the AAV2 genome (e.g.,new sequence would start at nu 3790 and 3962, respectively), or thecorresponding site of other AAV serotypes as known by those skilled inthe art. These positions correspond to insertions following amino acid529 and 586, respectively, of the AAV2 capsid (Met #1 of Vp1 as aminoacid 1; Table 2). In particular embodiments, there will be missensemutation at nucleotides 3790-3792 (Glu→Ile) or at nucleotides 3960-3961(Gly→Val), respectively, due to the creation of a restriction site aspart of the cloning strategy. In preferred embodiments of the invention,a targeting insertion at nu 3789 or 3961 is combined with the 3761mutation, which results in loss of heparin binding, to create a targetedcapsid or parvovirus.

In other preferred embodiments an insertion or substitution (preferably,insertion) is made in the AAV2 capsid at nucleotides 3753, 3858, 3960,or 3987 (new sequence beginning at the next nucleotide), or thecorresponding sites in AAV of other serotypes. These sites correspond toinsertions or substitutions following amino acids 517, 552, 586, or 595,respectively, of the AAV2 capsid (Met #1 of Vp1 as amino acid 1; Table2), or the corresponding sites in AAV capsids of other serotypes asknown by those skilled in the art.

In other preferred embodiments, the insertion or substitution is madefollowing amino acid 517, 529, 552, 586 or 595 of AAV capsids of otherserotypes, e.g. (1, 2, 3, 5 or 6).

There is no particular lower or upper limit to the length of the aminoacid sequence that may be inserted or substituted into the virus capsid,as long as the targeted or modified parvovirus capsid retains thedesired properties (e.g., assembly, packaging, infectivity). Theexogenous amino acid sequence may be as short as 100, 50, 20, 16, 12, 8,4 or 2 amino acids in length. Similarly, the exogenous amino acidsequence to be inserted/substituted into the parvovirus capsid may be aslong as 2, 5, 10, 12, 15, 20, 50, 100, 200, 300 or more amino acids. Inparticular embodiments, the exogenous amino acid sequence encodes anentire protein. Preferably, the exogenous amino acid sequence that isinserted/substituted into the parvovirus capsid is expressed on theoutside surface of the modified parvovirus capsid.

The present invention further provides targeted parvovirus capsidproteins, whereby a targeting sequence(s) is inserted or substitutedinto a parvovirus capsid protein, as described above. The targetedparvovirus capsid protein confers an altered tropism upon a virus vectoror virus capsid (preferably, a parvovirus vector or capsid)incorporating the targeted parvovirus capsid protein therein as comparedwith the tropism of the native virus vector or virus capsid in theabsence of the targeted parvovirus capsid protein. Likewise, modifiedcapsid proteins (modifications as described above for parvoviruses) areanother aspect of the invention. The modified capsid protein may beincorporated into a parvovirus capsid or particle, e.g., to facilitatepurification and/or detection thereof or for the purposes of antigenpresentation.

Further provided are targeted and/or modified parvovirus capsids asdescribed in more detail above in connection with chimeric parvoviruscapsids. In particular embodiments, the present invention providestargeted parvovirus “capsid vehicles”, as has been described for AAVcapsids, e.g., U.S. Pat. No. 5,863,541.

Molecules that may be packaged by the inventive parvovirus capsids andtransferred into a cell include recombinant AAV genomes, which mayadvantageously may then integrate into the target cell genome, and otherheterologous DNA molecules. RNA, proteins and peptides, or small organicmolecules, or combinations of the same. Heterologous molecules aredefined as those that are not naturally found in an parvovirusinfection, i.e., those not encoded by the parvovirus genome. In apreferred embodiment of the present invention, a DNA sequence to beencapsidated may be linked to an AAV ITR sequence that contains theviral packaging signals, which may increase the efficiency ofencapsidation and/or targeted integration into the genome.

The invention is further directed to the association of therapeuticallyuseful molecules with the outside of the inventive parvovirus capsidsfor transfer of the molecules into host target cells. Such associatedmolecules may include DNA, RNA, carbohydrates, lipids, proteins orpeptides. In one embodiment of the invention the therapeutically usefulmolecules is covalently linked (i.e., conjugated or chemically coupled)to the capsid proteins. Methods of covalently linking molecules areknown by those skilled in the art.

The targeted and/or modified parvovirus capsid proteins, capsids, andvirus particles of the invention find use for raising antibodies againstthese novel capsid structures. Alternatively, an exogenous amino acidsequence may be inserted into the parvovirus capsid for antigenpresentation to a cell, e.g. for administration to a subject to producean immune response to the exogenous amino acid sequence. According tothis latter embodiment, it is not necessary that the exogenous aminoacid sequence also alter the tropism of the parvovirus.

It will be appreciated by those skilled in the art thatmodified/targeted viruses and capsids as described above may also bechimeric and/or hybrid parvoviruses as described in the precedingsections. Those skilled in the art will further appreciate that theinsertion mutants described herein include parvoviruses with othermodifications, e.g., deletion, insertion or missense mutations. Inaddition, the mutations may incidentally be introduced into theparvovirus capsid or rAAV genome as a result of the particular cloningstrategy employed.

Parvoviruses, AAV, and rAAV genomes are as described above with respectto hybrid parvoviruses. The present invention also provides cloningvectors, transcomplementing packaging vectors, packaging cells, andmethods for producing the modified and/or targeted rAAV particlesdescribed above. In general, helpers, packaging cells, and methods forproducing the targeted or modified parvoviruses are as described abovewith respect to hybrid and chimeric viruses. In addition, at least oneof the cap genes (encoded by the rAAV genome, a packaging vector, or thepackaging cell) has inserted or substituted therein at least one nucleicacid sequence encoding an exogenous targeting sequence (as describedabove) or an exogenous amino acid sequence (as described above, e.g.,for purification, detection or antigen presentation).

IV. Gene Transfer Technology.

The methods of the present invention provide a means for deliveringheterologous nucleic acid sequences into a broad range of host cells,including both dividing and non-dividing cells. The vectors and otherreagents, methods and pharmaceutical formulations of the presentinvention are additionally useful in a method of administering a proteinor peptide to a subject in need thereof, as a method of treatment orotherwise. In this manner, the protein or peptide may thus be producedin vivo in the subject. The subject may be in need of the protein orpeptide because the subject has a deficiency of the protein or peptide,or because the production of the protein or peptide in the subject mayimpart some therapeutic effect, as a method of treatment or otherwise,and as explained further below.

In general, the present invention may be employed to deliver any foreignnucleic acid with a biological effect to treat or ameliorate thesymptoms associated with any disorder related to gene expression.Illustrative disease states include, but are not limited to: cysticfibrosis (and other diseases of the lung), hemophilia A, hemophilia B,thalassemia, anemia and other blood disorders, AlDs, Alzheimer'sdisease, Parkinson's disease, Huntington's disease, amyotrophic lateralsclerosis, epilepsy, and other neurological disorders, cancer, diabetesmellitus, muscular dystrophies (e.g., Duchenne, Becker), Gaucher'sdisease, Hurler's disease, adenosine deaminase deficiency, glycogenstorage diseases and other metabolic defects, retinal degenerativediseases (and other diseases of the eye), diseases of solid organs(e.g., brain, liver, kidney, heart), and the like.

Gene transfer has substantial potential use in understanding andproviding therapy for disease states. There are a number of inheriteddiseases in which defective genes are known and have been cloned. Insome cases, the function of these cloned genes is known. In general, theabove disease states fall into two classes: deficiency states, usuallyof enzymes, which are generally inherited in a recessive manner, andunbalanced states, at least sometimes involving regulatory or structuralproteins, which are inherited in a dominant manner. For deficiency statediseases, gene transfer could be used to bring a normal gene intoaffected tissues for replacement therapy, as well as to create animalmodels for the disease using antisense mutations. For unbalanced diseasestates, gene transfer could be used to create a disease state in a modelsystem, which could then be used in efforts to counteract the diseasestate. Thus the methods of the present invention permit the treatment ofgenetic diseases. As used herein, a disease state is treated bypartially or wholly remedying the deficiency or imbalance that causesthe disease or makes it more severe. The use of site-specificintegration of nucleic sequences to cause mutations or to correctdefects is also possible.

The instant invention may also be employed to provide an antisensenucleic acid to a cell in vitro or in vivo. Expression of the antisensenucleic acid in the target cell diminishes expression of a particularprotein by the cell. Accordingly, antisense nucleic acids may beadministered to decrease expression of a particular protein in a subjectin need thereof. Antisense nucleic acids may also be administered tocells in vitro to regulate cell physiology, e.g., to optimize cell ortissue culture systems. The present inventiori is also useful to deliverother non-translated RNAs, e.g., ribozymes (e.g., as described in U.S.Pat. No. 5,877,022), RNAs that effect spliceosome-mediatedtrans-splicing (Puttaraju et al., (1999) Nature Biotech. 17:246), or“guide” RNAs (see, e.g., Gorman et a., (1998) Proc. Nat. Acad. Sci. USA95:4929; U.S. Pat. No. 5,869,248 to Yuan et al.) to a target cell.

Finally, the instant invention finds further use in diagnostic andscreening methods, whereby a gene of interest is transiently or stablyexpressed in a cell culture system, or alternatively, a transgenicanimal model.

V. Subjects, Pharmaceutical Formulations, Vaccines, and Modes ofAdministration.

The present invention finds use in both veterinary and medicalapplications. Suitable subjects include both avians and mammals, withmammals being preferred. The term “avian” as used herein includes, butis not limited to, chickens, ducks, geese, quail, turkeys and pheasants.The term “mammal” as used herein includes, but is not limited to,humans, bovines, ovines, caprines, equines, felines, canines,lagomorphs, etc. Human subjects are the most preferred. Human subjectsinclude fetal, neonatal, infant, juvenile and adult subjects.

In particular embodiments, the present invention provides apharmaceutical composition comprising a virus particle of the inventionin a pharmaceutically-acceptable carrier or other medicinal agents,pharmaceutical agents, carriers, adjuvants, diluents, etc. Forinjection, the carrier will typically be a liquid. For other methods ofadministration, the carrier may be either solid or liquid, such assterile, pyrogen-free water or sterile pyrogen-free phosphate-bufferedsaline solution. For inhalation administration, the carrier will berespirable, and will preferably be in solid or liquid particulate form.As an injection medium, it is preferred to use water that contains theadditives usual for injection solutions, such as stabilizing agents,salts or saline, and/or buffers.

In other embodiments, the present invention provides a pharmaceuticalcomposition comprising a cell in which an AAV provirus is integratedinto the genome in a pharmaceutically-acceptable carrier or othermedicinal agents, pharmaceutical agents, carriers, adjuvants, diluents,etc.

By “pharmaceutically acceptable” it is meant a material that is notbiologically or otherwise undesirable, e.g., the material may beadministered to a subject without causing any undesirable biologicaleffects. Thus, such a pharmaceutical composition may be used, forexample, in transfection of a cell ex vivo or in administering a viralparticle or cell directly to a subject.

The parvovirus vectors of the invention maybe administered to elicit animmunogenic response (e.g., as a vaccine). Typically, vaccines of thepresent invention comprise an immunogenic amount of infectious virusparticles as disclosed herein in combination with apharmaceutically-acceptable carrier. An “immunogenic amount” is anamount of the infectious virus particles that is sufficient to evoke animmune response in the subject to which the pharmaceutical formulationis administered. Typically, an amount of about 1³ to about 10¹⁵ virusparticles, preferably about 10⁴ to about 10¹⁰, and more preferably about10⁴ to 10⁶ virus particles per dose is suitable, depending upon the ageand species of the subject being treated, and the immunogen againstwhich the immune response is desired. Subjects and immunogens are asdescribed above.

The present invention further provides a method of delivering a nucleicacid to a cell. For in vitro methods, the virus may be administered tothe cell by standard viral transduction methods, as are known in theart. Preferably, the virus particles are added to the cells at theappropriate multiplicity of infection according to standard transductionmethods appropriate for the particular target cells. Titers of virus toadminister can vary, depending upon the target cell type and theparticular virus vector, and may be determined by those of skill in theart without undue experimentation. Alternatively, administration of aparvovirus vector of the present invention can be accomplished by anyother means known in the art.

Recombinant virus vectors are preferably administered to the cell in abiologically-effective amount. A “biologically-effective” amount of thevirus vector is an amount that is sufficient to result in infection (ortransduction) and expression of the heterologous nucleic acid sequencein the cell. If the virus is administered to a cell in vivo (e.g., thevirus is administered to a subject as described below), a“biologically-effective” amount of the virus vector is an amount that issufficient to result in transduction and expression of the heterologousnucleic acid sequence in a target cell.

The cell to be administered the inventive virus vector may be ofany-type, including but not limited to neural cells (including cells ofthe peripheral and central nervous systems, in particular, brain cells),lung cells, retinal cells, epithelial cells (e.g., gut and respiratoryepithelial cells), muscle cells, pancreatic cells (including isletcells), hepatic cells, myocardial cells, bone cells (e.g., bone marrowstem cells), hematopoietic stem cells, spleen cells, keratinocytes,fibroblasts, endothelial cells, prostate cells, germ cells, and thelike. Alternatively, the cell may be any progenitor cell. As a furtheralternative, the cell can be a stem cell (e.g., neural stem cell, liverstem cell). Moreover, the cells can be from any species of origin, asindicated above.

In particular embodiments of the invention, cells are removed from asubject, the parvovirus vector is introduced therein, and the cells arethen replaced back into the subject. Methods of removing cells fromsubject for treatment ex vivo, followed by introduction back into thesubject are known in the art. Alternatively, the rAAV vector isintroduced into cells from another subject, into cultured cells, or intocells from any other suitable source, and the cells are administered toa subject in need thereof.

Suitable cells for ex vivo gene therapy include, but are not limited to,liver cells, neural cells (including cells of the central and peripheralnervous systems, in particular, brain cells), pancreas cells, spleencells, fibroblasts (e.g., skin fibroblasts), keratinocytes, endothelialcells, epithelial cells, myoblasts, hematopoietic cells, bone marrowstromal cells, progenitor cells, and stem cells.

Dosages of the cells to administer to a subject will vary upon the age,condition and species of the subject, the type of cell, the nucleic acidbeing expressed by the cell, the mode of administration, and the like.Typically, at least about 10² to about 10^(8,) preferably about 10³ toabout 10⁶ cells, will be administered per dose. Preferably, the cellswill be administered in a “therapeutically-effective amount”.

A “therapeutically-effective” amount as used herein is an amount of thatis sufficient to alleviate (e.g., mitigate, decrease, reduce) at leastone of the symptoms associated with a disease state. Alternativelystated, a “therapeutically-effective” amount is an amount that issufficient to provide some improvement in the condition of the subject.

A further aspect of the invention is a method of treating subjects invivo with the inventive virus particles. Administration of theparvovirus particles of the present invention to a human subject or ananimal in need thereof can be by any means known in the art foradministering virus vectors.

Exemplary modes of administration include oral, rectal, transmucosal,topical, transdermal, inhalation, parenteral (e.g., intravenous,subcutaneous, intradermal, intramuscular, and intraarticular)administration, and the like, as well as direct tissue or organinjection, alternatively, intrathecal, direct intramuscular,intraventricular, intravenous, intraperitoneal, intranasal, orintraocular injections. Injectables can be prepared in conventionalforms, either as liquid solutions or suspensions, solid forms suitablefor solution or suspension in liquid prior to injection, or asemulsions. Alternatively, one may administer the virus in a local ratherthan systemic manner, for example, in a depot or sustained-releaseformulation.

In particularly preferred embodiments of the invention, the nucleotidesequence of interest is delivered to the liver of the subject.Administration to the liver may be achieved by any method known in theart, including, but not limited to intravenous administration,intraportal administration, intrabiliary administration, intra-arterialadministration, and direct injection into the liver parenchyma.

Preferably, the cells (e.g., liver cells) are infected by a recombinantparvovirus vector encoding a peptide or protein, the cells express theencoded peptide or protein and secrete it into the circulatory system ina therapeutically-effective amount (as defined above). Alternatively,the vector is delivered to and expressed by another cell or tissue,including but not limited to, brain, pancreas, spleen or muscle.

In other preferred embodiments, the inventive parvovirus particles areadministered intramuscularly, more preferably by intramuscular injectionor by local administration (as defined above). In other preferredembodiments, the parvovirus particles of the present invention areadministered to the lungs.

The parvovirus vectors disclosed herein may be administered to the lungsof a subject by any suitable means, but are preferably administered byadministering an aerosol suspension of respirable particles comprised ofthe inventive parvovirus vectors, which the subject inhales. Therespirable particles may be liquid or solid. Aerosols of liquidparticles comprising the inventive parvovirus vectors may be produced byany suitable means, such as with a pressure-driven aerosol nebulizer oran ultrasonic nebulizer, as is known to those of skill in the art. See,e.g., U.S. Pat. No. 4,501,729. Aerosols of solid particles comprisingthe inventive virus vectors may likewise be produced with any solidparticulate medicament aerosol generator, by techniques known in thepharmaceutical art.

Dosages of the inventive parvovirus particles will depend upon the modeof administration, the disease or condition to be treated, theindividual subject's condition, the particular virus vector, and thegene to be delivered, and can be determined in a routine manner.Exemplary doses for achieving therapeutic effects are virus titers of atleast about 10⁵, 10⁶, 10⁷, 10⁸, 10⁹, 10¹⁰, 10¹¹, 10¹², 10³, 10¹⁴, 10¹⁵transducing units or more, preferably about 10⁸-10¹³ transducing units,yet more preferably 10¹² transducing units.

In particular embodiments of the invention, more than one administration(e.g., two, three, four, or more administrations) may be employed toachieve therapeutic levels of gene expression. According to thisembodiment, and as described above, it is preferred to use parvovirusvectors having different antigenic properties for each administration toobviate the effects of neutralizing antibodies. As described above, inparticular embodiments of the invention, the hybrid and chimericparvoviruses of the present invention are administered to circumventneutralizing antibodies in the subject to be treated or to prevent thedevelopment of an immune response in the subject. The subject may bepresented with seemingly new virus vectors by packaging the rAAV genomewithin an array of hybrid or chimeric parvovirus capsids.

The foregoing discussion also pertains to pharmaceutical formulationscontaining parvovirus capsids and other reagents of the invention aswell as methods of administering the same.

In summary, the parvovirus vectors, reagents, and methods of the presentinvention can be used to direct a nucleic acid to either dividing ornon-dividing cells, and to stably express the heterologous nucleic acidtherein. Using this vector system, it is now possible to introduce intocells, in vitro or in vivo, genes that encode proteins that affect cellphysiology. The vectors of the present invention can thus be useful ingene therapy for disease states or for experimental modification of cellphysiology.

Having now described the invention, the same will be illustrated withreference to certain examples, which are included herein forillustration purposes only, and which are not intended to be limiting ofthe invention.

EXAMPLE 1 AAV Vectors

All production of AAV vectors used in these investigations utilized thevector production scheme as described in Ferrari et al., (1997) NatureMed. 3:1295 and Xiao et al., (1998) J. Virology 72:2224. Utilizing atransient transfection procedure, rAAV devoid of adenovirus has beengenerated. Id. This protocol utilizes an adenovirus DNA genome that hasbeen incapacitated for viral replication and late gene expression. Themini Ad plasmid while unable to replicate and produce progeny, is stillviable for adenovirus gene expression in 293 cells. Using thisconstruct, the AAV packaging strategy involving new AAV helper plasmid(pAAV/Ad ACG) and AAV vector DNA (sub 201) has been successfullycomplemented (Samulski et al., (1989) J of Virology 63:3822). This newconstruct typically generates rAAV of 10⁷-10⁹/10 cm dish of 293 cells(Xiao et al., (1998) J. Virology 72:2224). Efficient gene delivery isobserved in muscle, brain and liver with these vectors in the completeabsence of Ad.

EXAMPLE 2 Cells and Viruses

Human 293 and HeLa cells were maintained at 37° C. with 5% CO₂saturation in 10% fetal bovine serum (Hyclone) in Dulbecco's modifiedEagles medium (Gibco BRL), with streptomycin and penicillin (LinebergerComprehensive. Cancer Center, Chapel Hill, N.C.). Four×10⁶293 cells wereplated the day before transfection onto a 10 cm plate. Cells weretransfected by both calcium phosphate (Gibco BRL) or Superfection(Qiagene) according to manufacturers specifications. The insertionalmutant packaging plasmids, described below, were transfected along withpAB11 containing the CMV driven Lac Z gene with a nuclear localizationsignal. For each transfection the same amount of packaging plasmid (12μg) and pAB11 (8 μg) were used for each 10 cm plate. For eachtransfection an additional plate was used containing the transgeneplasmid only to assess transformation efficiencies. After transfectionthe cells were infected with helper virus Ad5 d/309 at an MOI of 5, and48 hours later the cells were lysed and the virus purified.

Recombinant virus was purified using cesium chloride isopycnic oriodixanol gradients. In both cases cells were centrifuged at 1500 rpms(Sorvall RT 6000B) for ten minutes at 4° C. Proteins were precipitatedfrom the supernatant using ammonium sulfate (30% w/v) and resuspended in1× Phosphate-buffered saline (PBS) (137 mM NaCl, 2.7 mM KCl, 4.3 mMNa₂HPO₄ 7H₂O, 1.4 mM KH₂PO₄). The cell pellet was resuspended in 1×PBScontaining 0.1 mg/ml DNase I (Boehringer Mannheim) lysed by threefreeze-thaw cycles, combined with the protein portion of thesupernatant, and incubated at 37° C. for 30 minutes. This material wassubjected to sonication (Branson Sonifier 250, VWR Scientific), 25bursts at 50% duty, output control 2. Cell debris was removed bycentrifugation (Sorvall RT 6000B). To each milliliter of supernatant 0.6g of cesium chloride (CsCl) was added and the solution was centrifugedfor 12-18 hours (Beckman Optima TLX ultracentrifuge) in a TLS 55 rotorat 55,000 rpms. Alternatively, the supernatant was layered on top of anlodixanol (OptiPrep-Nycomed Pharma As, Oslo, Norway) gradient of 60%,45%, 30% and 15%. This gradient was centrifuged in a Beckman Optima TLXultracentrifuge using a TLN 100 rotor at 100,000 rpm for one hour.Fractions were recovered from these gradients and 10 μl from eachfraction were utilized for dot blot hybridization to determine whichfraction contained the peak protected virion (see Example 5).

EXAMPLE 3 Construction of AAV Packaging Plasmids

The capsid domain of pAAV/Ad was cloned into pBS+ (Stratagene) usingHind III, resulting in pAV2Cap. Partial digestion of pAV2Cap using therestriction enzymes Hae III, Nla IV, and Rsa I and gel purification ofthe unit length DNA fragment resulted in the isolation of the startingmaterial for cloning. The aminoglycoside 3′-phosphotransferase gene,conferring kanamycin resistance (kan^(r)), from pUC4K (Pharmacia)digested with Sal I was flanked by linkers containing Nae I and Eco RVsites, a Sal I overhang at one end and an Eco RI overhang at the otherend (top 5′-MTTCGCCGGCGATATC-3′, SEQ ID NO:6, bottom5′-TCGAGATATCGCCGGC-3′, SEQ ID NO:7). This fragment was cloned into theEco RI site of pBluescript SK+ (Stratagene). Digestion with Nae Ireleased the kan^(r) gene, and this fragment was ligated into thepAV2Cap partials. The resulting plasmids were screened for insertioninto the capsid domain and, then digested with Eco RV to remove thekan^(r) gene leaving the twelve base pair insertion 5′-GGCGATATCGCC-3′(SEQ ID NO:8) within the capsid domain. Multiple enzyme digests and DNAsequencing were used to determine the position of the 12 bp insertionwithin the capsid coding domain. The enzyme digests include Eco RV/BanII, Eco RV/Bst NI, Eco RV/Pst II and Eco RV/Hind III. The capsid domainof the resulting plasmids were digested with Asp718 and subcloned intothe pACG2 packaging plasmid (Li et al., 1997 J. Virology 71:5236), withthe exception of one Nla IV clone that overlapped the 3′-Asp718 site.This insertion mutant was cloned into pAAV/Ad using a Hind III/Nsi Idigestion.

EXAMPLE 4 Western Blotting

Cell lysates after freeze thaw lysis and sonication was centrifuged toremove large cell debris. Twenty microliters of supernatant wasimmediately added to 20 μl of 2×SDS gel-loading buffer containingdithiothreitol and boiled for five minutes. Proteins were analyzed bySDS polyacrylamide gel electrophoresis and transferred to nitrocelluloseelectrophoretically. The nitrocellulose membranes were immunoblottedusing the anti-Vp3 monoclonal antibody B1 (a generous gift from JurgenA. Kleinschmidt). Each of the insertion mutants was tested at leasttwice by Western blot analysis. The secondary anti-mouse HorseradishPeroxidase IgG was used to indirectly visualize the protein by enhancedchemiluminescence (ECL-Amersham). The Western blots were scanning fromenhanced chemiluminescence exposed BioMax film (Kodak) into AdobePhotoShop and analyzed by ImageQuaNT software (Molecular Dynamics Inc.).

Viral proteins were visualized by Western blotting followed byimmunoblotting as described above. Between 1.0×10⁹ and 2.5×10⁹ viralparticles were used for each sample. The virus was isolated from thepeak cesium gradient fraction as determined by dot blot, and dialysedagainst 0.5×PBS containing 0.5 mM MgCl₂ prior to polyacrylamide gelelectrophoresis.

EXAMPLE 5 Titration of Recombinant Virus

Fractions from CsCl gradients were obtained by needle aspiration. Therefractive index was obtained using a refractometer (Leica Mark II), andthe index was used to determine the density of fractions. Aliquots of 10μl from fractions between 1.36 g/ml and 1.45 g/ml were tested for thepresence of protected particles by dot blot hybridization. The aliquotswere diluted 1:40 in viral dilution buffer (50 mM Tris HCl, 1 mM MgCl₂,1 mM CaCl₂ 10 [2 g/ml RNase, 10 μg/ml DNase) and incubated at 37° C. for30 minutes. To the samples Sarcosine (final concentration 0.5%) and EDTA(final 10 mM) were added and incubated at 70° C. for 10 minutes.Proteinase K (Boehringer Mannheim) was added to a final concentration of1 mg/ml and the samples were incubated at 37° C. for two hours.Following this incubation the samples were denatured in NaOH (350 mMfinal) and EDTA (25 mM final). The samples were applied to equilibratednytran (Gene Screen Plus, NEN Life Science Products) using a dot blotmanifold (Minifold I, Schleicher and Schuell). The membrane was probedwith a random primed (Boehringer Mannheim) ³²P-dCTP labeled Lac Z DNAfragment. The membranes were exposed to film (BioMax MR, Kodak) or tophosphor imagining screens (Molecular Dynamics) and intensity estimateswere done using ImageQuant software (Molecular Dynamics). Peak fractionof virus were then dialysed in 1×PBS for transducing titer.

Transductions titers were determined by histochemical staining for Lac Zactivity. HeLa cells had been infected with Ad d/309 at a multiplicityof infection of five for one hour. The cells were then washed with 1×PBSand fresh medium was added. Aliquots of virus from peak fractions,equivalent to 1.75×10⁸ particles were used to infect Hela cells. Twentyto twenty-four hours later cells were washed with 1×PBS, fixed (2%formaldehyde 0.2% gluteraldehyde in 1×PBS), washed, and stained with5′-Bromo-4-chloro-3-indoly-β-D-galactopyranoside (Gold Bio Technology)dissolved in N,N-dimethylformamide (Sigma) diluted to 1 mg/ml in 1×PBSpH7.8, 5 mM potassium ferricyanide, 5 mM potassium ferrocyanide, 2 mMMgCl2 at 37° C. for 12-24 hours. Stained HeLa cells were counted in ten400× microscope fields. The transducing number was determined byaveraging the number of stained cells in ten fields and multiplying bythe number of fields on the plate and dividing that number by the numberof nanograms of protected template.

EXAMPLE 6 Electron Microscopy

Peak fractions of rAAV with wildtype virion or mutagenized virions weredialysed in 0.5×PBS containing 0.5 mM MgCl₂. The virus was placed on a400 mesh glow discharged carbon grid by inverting on a 10 μl drop ofvirus for ten minutes at room temperature. Followed by three 1×PBSwashes for one minute each. The virus was stained in 1% Phosphotungsticacid for one minute. Specimens were visualized using a Zeiss EM 910electron microscope.

EXAMPLE 7 Heparin Agarose Binding Assay

Recombinant virus containing wild-type capsids or insertion in thecapsids were dialysed against 0.5×PBS containing 0.5 mM MgCl₂. Onehundred microliters of each virus was bound to 100 μl of heparin agarosetype 1 (H-6508 Sigma, preequilibrated in twenty volumes of 0.5×PBScontaining 0.5 mM MgCl₂) at room temperature for one hour in a 1.5 mlmicrofuge tube. After each step, binding washes and elutions sampleswere centrifuged at 2000 rpm (Sorvall MC 12V) for two minutes to collectsupernatant. Samples were washed six times with 0.5 ml of 0.5×PBScontaining 0.5 mM MgCl₂, and the supernatant collected. Samples wereeluted in three steps of 100 μl volumes containing 0.5, 1.0 and 1.5MNaCl in 0.5×PBS containing 0.5 mM MgCl₂ and the supernatant collected.For each sample 20 μl of supernatant from each step was used for dotblot hybridization. The 100% bound control was an internal standardequivalent to one fifth of each input virus used in the dot blot. Theheparin agarose viral mixtures were washed six times with 0.5×PBS 0.5 mMMgCl₂ in volumes that resulted in a 1:15625 dilution.

EXAMPLE 8 Construction of Insertional Mutations in rAAV2

In order to evaluate the role of AAV structural proteins in assembly andinfectivity, we generated a collection of capsid linker insertionmutants. A 2.8 kb Hind III fragment of pAAV/Ad (Samulski et al., (1989)J. Virology 63:3822) containing the sequences coding for the capsiddomain of AAV2 was subcloned into pBS+. This plasmid, pAV2Cap, was usedfor partial digestion with Hae III, Nla IV, and Rsa I to generate asubstrate for capsid specific insertions (FIG. 1). These three DNArestriction enzymes constitute 43 sites that span across the AAV-2capsid coding sequence of which only 4 overlap. To efficiently identifyclones that contain insertions, a kanamycin resistance gene (Kan^(r))flanked by a novel oligo (Nae IlEcoR V) was ligated with partiallydigested, full-length, linearized pAV2Cap (see Example 3 and FIG. 1).Using ampicillin and kanamycin selection in E. coli, insertion mutantswere identified and the Kan^(r) gene was shuttled out of the capsidcoding region by digesting and religation with the nested pair of Eco RVsites (see Example 3). This resulted in a specific linker insertion of12 base pair (bp) carrying a single copy of the unique Eco RV site inthe capsid coding sequences. The exact positions of the linker insertionwere further refined by restriction enzyme digestions, and in six casessequencing (data not shown). The position of insertion mutants areidentified by the first letter of the enzyme used in the partialdigestion followed by the nucleotide position of the restriction site inthe AAV2 genome, for example Nla IV 4160 would be N4160.

The capsid coding sequence from these mapped insertion mutants weresubcloned into the helper vectors pACG2 or pAAV/Ad for biologicalcharacterization in vivo (FIG. 1) (Li et al., (1997) J. Virology71:5236; Samulski et al., (1989) J. Virology 63:3822). Sequence analysispredicts that this 12 base pair insertion cannot result in a terminationcodon for any of the 43 insertion sites (Table 1). Owing to the randomnature of the cut site for the enzymes (Hae III, Nla IV, and Rsa I) withrespect to codon frame usage and the degeneracy of the Nla IVrecognition sequence, the 12 bp linker resulted in the insertion of theamino acids GDIA in frame 1 and AISP in frame 3 for all three enzymes,while insertions in frame 2 resulted in WRYRH for Rsa I, GRYRP for HaeIII, and both GRYRP and GRYRH for Nla IV. The bolded amino acid in theseexamples represents missense mutation (Table 1). The mutant helperconstructs, pACG2^(IN), were individually transfected into 293 cellsalong with an AAV reporter vector, containing the β-galactosidase genein Adenovirus d/309 (MOI=5) infected cells (Li et al., (1997) J.Virology 71:5236). The transfected cells were then assayed for capsidexpression and recombinant virus production (see Example 5; Li et al.,(1997) J. Virology 71:5236). TABLE 1 Physical Structure and Phenotype ofAAV2 Capsid Insertion Mutants Position¹ Capsid Heparin Electron insertedsubmit Frame² Dot blot³ Infectious⁴ Agarose⁵ Microscope Phenotype AminoAcid⁶ H2285 VP1 3 2.8 × 10⁷ − + normal Class II AISP R2356 VP1 2 1.4 ×10⁸ + + N.D. Class III WRYRH N2364 VP1 1 − − N.D. N.D. Class I GDIAH2416 VP1 2 1.4 × 10⁷ − + N.D. Class II GRYRP H2591 VP1 3 1.4 × 10⁷ + +normal Class III AISP H2634 VP2 1 2.8 × 10⁷ − + normal Class II GDIAH2690 VP2 3 7.0 × 10⁶ + + normal Class III AISP R2747 VP2 3 − − N.D.N.D. Class I AISP H/N2944 VP3 2 1.4 × 10⁶  +* N.D. N.D. ClassII/IIIGRYRP N3317 VP3 3 1.4 × 10⁵ − N.D. N.D. Class II AISP R3391 VP3 2 − −N.D. N.D. Class I WRYRH N3561 VP3 1 − − N.D. N.D. Class I GDIA H3595 VP32 1.4 × 10⁶  +* N.D. abnormal Class II/III GRYRP H/N3761 VP3 3 1.4 × 10⁷− − normal Class II AISP H3766 VP3 2 2.8 × 10⁷ − N.D. N.D. Class IIGRYRP N4046 VP3 3 − − N.D. N.D. Class I AISP H/N4047 VP3 1 − − N.D. N.D.Class I GDIA N/R4160 VP3 3 1.4 × 10⁷ + + normal Class III AISP¹The letter refers to the restriction enzyme used in the partialdigestion and the number refers to nucleotide of the restriction site inthe AAV2 sequence.²Reading frame of the restriction site.³The particle number per microliter of sample. (−) = <10⁵ genomes.⁴Infections were done using 1.75 × 10⁸ particles of rAAV insertionmutants in adenovirus infected HeLa cells.⁵By batch binding and assayed by infection of HeLa cells (Class III) orby dot blot (Class II).⁶Amino acids differ depending on the frame of the insertion. The boldedamino acid is a missense mutation.

EXAMPLE 9 Analysis of Capsid Proteins

Before assaying for vector production using mutant capsid constructs incomplementation assays, each insertion mutant was tested for expressionof capsid subunits in 293 cells after transfection. The ability toproduce Vp1, Vp2, and Vp3 at normal stoichiometry would suggest thatlinker insertions did not alter capsid protein expression, or stability.Since the linker did not introduce stop codons, it was expected thateach insert would produce all three capsids. Forty-eight hours aftertransfection, cell lysates were analyzed by Western blot for AAVcapsids. The Western blot analysis in FIG. 2 is a representation ofinsertion mutant capsid expression in cell lysates. With the exceptionof H2634 (FIG. 2 lane 2), the stoichiometry of the three capsid subunitsdoes not appear significantly different than that of wild-type controls(FIG. 2 compare lanes 1,3-7 to lane 8). By this assay, insertion mutantH2634 appears to only produce Vp3 subunits (FIG. 2; lane 2). In longerexposures, the minor capsid subunits in FIG. 4 lanes 4 and 5 wereapparent (data not shown).

EXAMPLE 10 Mutant Capsid Ability to Produce Stable Virions

To test for the production of stable virions that protect a vectorgenome from DNase digestion, we subjected the cell lysates to cesiumchloride (CsCl) gradient centrifugation. Virus densities were measuredby refractometry, and aliquots from appropriate fractions were subjectedto dot blot hybridization (FIG. 3 a). Based on this analysis, particlesthat package intact recombinant genomes should display a buoyant densitysimilar to wild-type and be resistant to DNase treatment, with theexception of H2944 which has a buoyant density slightly higher than wildtype. Results for this assay separated insertion mutants into twoclasses. Class I mutants were negative for protecting the viral genome,while class II mutants appeared normal for packaging and protecting thevector substrate (Table I).

All class II mutants had a buoyant density within the range of wild-typeAAV2 capsids (FIG. 3 a). By dot blot analysis, N2944 packaged therecombinant genome but migrated to a position of slightly greaterdensity than wild type in isopycnic gradients (FIG. 3 a, N2944 lane 3).A number of insertion mutants (7) did not package DNA by this assaywhich had a sensitivity of <1×10⁵ particles/μl (see methods forquantitation) (Table 1). Whether these mutants were defective inpackaging or unstable during purification remains to be determined.

EXAMPLE 11 Infectivity of Class II Insertion Mutants

Virions generated by insertion mutants in the complementation assay weretested for infectivity by monitoring transduction of LacZ reporter genein human cells. Using viral titers derived from dot blot hybridization,HeLa cells were infected with mutant virus stocks at equivalent particlenumbers.

Twenty-four hour post infection, expression of the transgene wasdetected by X-gal staining. A representative figure of this analysis isshown (FIG. 3 b) and all mutants assayed are presented in Table 1. Inthis assay, wild-type virions transduced 5.6×10⁵ HeLa cells/1.75×10⁸protected particles (FIG. 3 b). Based on the sensitivity of this assay,the range of infection efficiency for class II insertion mutant viruseswas from 0 to 1.6×10⁶ transducing units/1.75×10⁸ protected particles.Results from this analysis further subdivided the capsid insertionmutants from class II (normal for packaging and protecting the vectorsubstrate) into a class III phenotype (normal for packaging andprotecting the vector substrate and infectious virions). Two insertionmutants negative for infectivity and initially identified as class IImutants (N2944, H3595) based on CsCl purification and DNase protection,tested positive for viral transduction after purification using aniodixanol step gradient (Table 1). This virus purification technique isnot as harsh as CsCl and has been shown to increase virus recovery byten-fold (Zolotukhin et al., (1999) Gene Therapy 6:973). However, otherclass II mutants remained non-infectious after purification using aniodixanol step gradient (data not shown). Although we determined thatinsertion mutant viruses N2944 and H3595 were infectious using the Lac Ztransduction assay, it should be noted that these mutants resulted inlow infectious titers (1×10² transducing units/ng) similar to previouslypublished lip mutants (Hermonat et al, (1984) J. Virology 51:329).

EXAMPLE 12 Electron Microscopy of Class II and Class III Mutants

To further characterize class II and III rAAV2 insertion mutants forbiological differences, we visualized mutant particles by electronmicroscopy (EM). The EM analysis revealed only gross morphology of theinfectious class III viruses, which were indistinguishable fromwild-type virions (Compare FIGS. 4 a, and 4 b,c). Whereas distinctdifferences were observed between class II/III mutant virus H3595 whencompared to wild-type virions (FIGS. 4 a, and 4 f-bottom four panels).EM images of H3595 revealed a slightly larger roughly pentagonaloutline, while wild-type virus appeared uniformed in size and washexagonal. Interestingly, class II mutant H2634, which was negative forVp1 or Vp2 by Western blot (FIG. 2 lane 2), appeared normal inmorphology by EM analysis (FIG. 4 d). Based on this analysis, virionmorphology alone is not sufficient to distinguish class II mutants fromclass III since small insertions within the capsids can result in eithernon-detectable (FIG. 4 b,c,d,e) or noticeable alterations in virionstructure (FIG. 4 f-bottom four panels). However, this approach was ableto provide additional data to our characterization of these linkerinsertion mutants (FIG. 4, compare a to f).

EXAMPLE 13 Capsid Ratio of Class II and Class III Virions

Rose et. al. (1971) established that AAV2 particles are composed of Vp1,Vp2, and Vp3 at a 1:1:20 ratio (Rose et al., (1971) J. Virology 8:766).In an effort to determine if class II and class III mutant virionsmaintained this ratio, Western blots were performed on the cesiumchloride purified virus. Purified viruses analyzed by Western blotshowed similar amounts of Vp3 in all mutants sampled (FIG. 5, Vp3arrow), between 1×10⁹ and 2.5×10⁹ viral particles were used for eachsample. The amounts of Vp2 and Vp1 are also nearly equivalent in alltest samples except H2634 where no minor capsid components were observed(FIG. 5, lane 5). The lack of minor capsid components for H2634 isconsistent with the Western results from cell lysate (FIG. 2). At thelimit of detection in this assay, the class II insertion mutant H2634appears to assemble AAV virions without Vp1 and Vp2, even though EManalysis suggest this mutant has normal morphology (FIG. 4 d).

EXAMPLE 14 Heparin Binding of Class II and Class III Mutants

Recently our lab established that AAV-2 uses a heparan sulfateproteoglycan as a primary receptor for infectivity (Summerford andSamulski, (1998) J. Virology 72:1438). To determine what role heparinbinding may have in class II particles inability to infect cells as wellas the ability of class III virus to bind heparin agarose, heparin batchbinding experiments were performed. Not surprisingly, all class IIImutants were positive for heparin binding, with the majority of viruseluting in the 1M NaCl₂ step (data not shown). To determine if loss ofinfectivity of class II mutant viruses was related to a lack of heparinbinding, batch binding experiments were analyzed by dot blothybridization (FIG. 6). For each of the viral samples tested, aninternal control to determine 100% bound was spotted on the filterindependent of heparin binding (FIG. 6; 100% bound). This allowed us todetermine percent virus retained, at each step of heparin purification.After binding to heparin agarose, samples were washed then eluted usingincreasing salt concentrations (see Example 7). Recombinant AAV2 withwild-type virion shells demonstrated 90% binding with 10% released inthe wash followed by 60% recovered in the elution buffer, and 20%remaining bound to heparin agarose (FIG. 6, lane 1). Class II mutantsH2285, H2416, and H2634 demonstrated similar binding and elutionprofiles (FIG. 6, lanes 2-4). However, class II mutant H3761 wasdistinct in its heparin agarose binding profile with the majority of thevirion in the binding buffer and the washes (FIG. 6, lane 5). Furtheranalysis is required to determine the reason for lack of Heparin bindingin this batch assay.

Interestingly, H2634 binds heparin agarose under these conditions, whichby Western blot does not carry detectable Vp1 or Vp2 subunits (FIG. 5,lane 4). The lack of Vp1 and Vp2 in H2634 along with its ability to bindheparin agarose suggest that the heparin binding domain may be locatedin Vp3 capsid proteins.

EXAMPLE 15 Linker Insertion Mutants

Insertion sequences encoding poly-lysine, poly-histidine, an RGD motif,or bradykinin were inserted into the linker mutants described inTable 1. We developed a PCR-based method of identifying insertions ofdifferent linkers into the coding domain of AAV2 capsid gene. Briefly,one primer was used outside of the capsid coding region and one thatcorresponds exactly to the linker. If the linker is in the correctorientation, then the PCR product is of a size that is dependent on theinsertion mutant's position.

After transformation of the ligation reactions, bacterial colonies werepicked with a pipet tip and dipped 4-5 times into a well of a 96-wellplate containing LB-medium with antibiotic. The pipet tip was thenplaced in a well of a 96-well plate containing PCR reaction buffer. ThePCR products were run out on an agarose gel, and positive clones wereidentified. This information indicated the orientation and the positionof the insertion mutant with respect to the outside primer.

The LB-medium that is in the corresponding well was used as the PCRpositives, and this material was grown in a larger (5 mL) volume. Afteran overnight growth phase, the plasmid DNA was isolated and digestedwith an enzyme that restricts the DNA 15 times (Bst NI). These digestionproducts were separated on a 5-6% acrylamide gel. Depending upon thesize of the linker insertion and the size of the correspondinguninserted fragment, the number of inserts is determined. Thus, withintwo days of ligating the linker into the insertion site, we know theorientation and number of linker insertion, and we have sufficient DNAto transfect a 10 cm plate for virus production.

pACG2 (Li et al., 1997 J. Virology 71:5236) without any insertion whendigested with Bst NI yields fragments of:

3900 bp

1121 bp

1112 bp

445 bp—H2944 shifts

347 bp—H2634, H2690 shifts

253 bp—H3595 shifts

215 bp—R2356, H2416 shifts

121 bp

111 bp

64 bp

63 bp—H2285 shifts

33 bp—H2591 shifts

13 bp

9 bp

The band shifts with the different insertion mutants are also indicated.

pACG2 without any insertion when digested with Ban I yields fragmentsof:

2009 bp

1421 bp

168 bp

843 bp—H4047 shifts

835 bp

734 bp—H2634 shifts

464 bp

223 bp

218 bp

211 bp

50 bp

Each of the inserts contains the original 12 base pairs of the Eco RVsite. In addition, each of the linkers adds additional base pairs:

-   -   RGD=36 bp+12=48 bp for a single insertion.    -   Bradykinin (BRDY)=69 bp+12=81 bp for a single insertion. Note:        The BRDY insert contains a BstNI site.    -   Histidine (8HIS)=51 bp+12=63 bp for a single insertion.    -   Poly Lysine (PLY)=63 bp+12=75 bp for a single insertion.

The outside primer is near the Hind III site and is called AAV2/4 5′.This primer can be used to amplify AAV serotypes 2 and 4.

Primer sequences used to produce epitope linkers into the originalinsertion mutants are given below. Note: Because there are three framesfor the insertion mutants there are three primer pairs for each primerset.

Histidine Primer Pairs: Frame 1: Top primer a 48 mer (SEQ ID NO:9):5′ -GCT AGC GGC GGA CAC CAT CAC CAC CAC CAT CAC CAC GGC GGA AGC GCT- 3′Bottom primer a 48 mer (SEQ ID NO:10): 5′ -AGC GCT TCC GCC GTG GTG ATGGTG GTG GTG ATG GTG TCC GCC GCT AGC- 3′ Frame 2: Top primer a 51 mer(SEQ ID NO:11): 5′ -AC GCT AGC GGC GGA CAC CAT CAC CAC CAC CAT GAC GACGGC GGA AGC GCT T- 3′ Bottom primer a 51 mer (SEQ ID NO:12): 5′ -A AGCGCT TCC GCC GTG GTG ATG GTG GTG GTG ATG GTG TCC GCC GCT AGC GT- 3′ Frame3: Top primer a 51 mer(SEQ ID NO:13): 5′ -G GGT TCC GGA GGG CAC CAC CATCAC CAC CAC CAT CAC GGA GGC GCC AGC GA- 3′ Bottom primer a 51 mer (SEQID NO:14): 5′ -TC GCT GGC GCC TCC GTG ATG GTG GTG GTG ATG GTG GTG CCCTCC GGA ACC C- 3′

Bradykinin Primer Pairs: Frame 1: Top primer a 60 mer (SEQ ID NO:15):5′ -GCC GGA TCC GGC GGC GGC TCC AGA CCC CCC GGG TTC AGC CCC TTC AGA TCCGGC GGC GCC- 3′ Bottom primer a 60 mer (SEQ ID NO:16): 5′ -GGC GCC GCCGGA TCT GAA GGG GCT GAA GCC GGG GGG TCT GGA GCC GCC GCC GGA TCC GGC- 3′Frame 2: Top primer a 69 mer (SEQ ID NO:17): 5′ -GA GGT TCA TGT GAC TGCGGG GGA AGA CCC CCT GGC TTC AGC CCA TTC AGA GGT GGC TGC TTC TGT GGC G-3′ Bottom primer a 69 mer (SEQ ID NO:18): 5′ -C GCC ACA GAA GCA GCC ACCTCT GAA TGG GCT GAA GCC AGG GGG TCT TCC CCC GCA GTC ACA TGA ACC TC- 3′Frame 3: Top primer a 60 mer (SEQ ID NO:19): 5′ -A GGT TCA TGT GAC TGCGGG GGA AGA CCC CCT GGC TTC AGC CCA TTC AGA GGT GGC TGC TTC TGT GGC GG-3′ Bottom primer a 60 mer (SEQ ID NO:20): 5′ -CC GCC ACA GAA GCA GCC ACCTCT GAA TGG GCT GAA GCC AGG GGG TCT TCC CCC GCA GTC ACA TGA ACC T- 3′

RGD Primer Pairs: Frame 1: Top primer a 36 mer (SEQ ID NO:21): 5′ -GGATCC TGC GAC TGC AGG GGC GAT TGT TTC TGC GGC- 3′ Bottom primer a 36 mer(SEQ ID NO:22): 5′ -GCC GCA GAA ACA ATC GCC CCT GCA GTC GCA GGA TCC- 3′Frame 2: Top primer a 36 mer (SEQ ID NO:23): 5′ -GA TCC TCG GAC TGC AGGGGC GAT TGT TTC TGC GGC G- 3′ Bottom primer a 36 mer (SEQ ID NO:24):5′ -C GCC GCA GAA ACA ATC GCC CCT GCA GTC GCA GGA TC-3′ Frame 3: Topprimer a 36 mer (SEQ ID NO:25): 5′ -A GGA TCC TGC GAC TGC AGG GGC GATTGT TTC TGC GG- 3′ Bottom primer a 36 mer (SEQ ID NO:26): 5′ -CC GCA GAAACA ATC GCC CCT GCA GTC GCA GGA TCC T- 3′ Polylysine primer pair: Note:only the frame three primer pair was made. Frame 3: Top primer a 63 mer(SEQ ID NO:27): 5′ -A GGT TCA TGT GAC TGC GGG GGA AAG AAG AAG AAG AAGAAG AAG GGC GGC TGC TTC TGT GGC GG- 3′ Bottom primer a 63 mer (SEQ IDNO:28): 5′ -CC GCC ACA GAA GCA GCC GCC CTT CTT CTT CTT CTT CTT CTT TCCCCC GCA GTC ACA TGA ACC T-3′ Outside primer AAV 2/4 5′ top primer (SEQID NO:29): 5′ -TGC CGA GCC ATC GAC GTC AGA CGC G- 3′

The RGD linker was inserted into the H2285, R2356, H2591, H2634, H2690,H/N3761, and H/N4047 mutants from Table 1.

The bradykinin linker was inserted into the H2285, H2416, H2591, H2634,H2690, H/N2944, and H/N3761 mutants from Table 1.

The poly-Lys linker was inserted into the H2285, H2591, H2690, andH/N3761 mutants from Table 1.

The poly-His linker was inserted into the H2285, H2416, H2591, H2634,H2690, H/N2944, N3561, H3766, and H/N4047 mutants from Table

EXAMPLE 16 Characterization of Insertion Mutants

The insertion mutants at site H2690 all have titers similar to theoriginal 12 bp insert. Using the ELISA assay and the anti-histidineantibody polyHis insertions into this site were shown to be displayed onthe surface of the virion.

The polyHis epitope was also shown to be on the surface when insertedinto site H2634. Interestingly, the Western blot analysis of the 12 bpinsertion at H2634 did not show any VP1 or VP2 subunits being formed. Ithas been determined that this insertion in VP2 is near the nuclearlocalization signal for the VP1 And VP2 subunits. It is possible thatthis domain was disrupted by the original insertion, and with theaddition of the 8-histidines the domain was repaired. Although the dotblot of this 8His virus showed the presence of viral particles, theseparticles were not infectious.

The insertion site H2591 is in VP1. Insertion of linker epitopes intothis site do not affect the titer any more than did the original 12 bpinsertion at this site (Table 1).

The insertion at site N4160 is in VP3 near the carboxy terminus. Thisinsertion mutant is of interest because the original 12 bp insertioninfects cell at an equivalent level as wild-type (Table 1).

Mutant R3317, which has been previously described in Table 1, appearednot to protect virions by dot blot analysis. Repeating this experimentwith a LacZ transgene, the same results were observed, i.e., noprotected particles. However, when using an independent clone and theGFP transgene (˜1000 bp smaller than LacZ) protected particles wereobserved. In addition, the GFP-expression virion transduced HeLa cellsat high levels, equivalent to wild-type. It is unclear why disparateresults were observed with different transgenes.

In addition, a linker encoding the respiratory syncitial virus heparinbinding domain is inserted into the H2690 mutant at a site thattolerates inserts without loss of viability (Table 1) to restore heparinbinding to this mutant.

EXAMPLE 17 Unique Restriction Site Mutants

Unique restriction sites within the capsid of AAV type 2 were made tofacilitate the generation of insertional mutants. The sites were chosenso that the mutations introduced into the nucleotide sequence of thecapsid were conservative, i.e., were not missense mutations or result instop codons. Amino acid positions 586, 529, 595, 552, and 517 (VP1methionine as amino acid #1) were chosen. For all of these positions,except 529, unique Hpa I sites were engineered. For the site at aminoacid 529, a unique Eco RV site was engineered. Each of these uniquerestriction sites results in an in-frame blunt ended digestion product.So frame 1 linkers were used to insert into these sites. Overlappingprimers were used to generate the unique sites, and outside primers wereused to generate the right and left fragments of the insertion.

The right fragment was then digested with Nsi I and either Eco RV or HpaI, and the left fragment with Hind III and either Eco RV or Hpa I. Wecloned these digestion products into the pACG vector that had alreadydigested with Hind III and Nsi I. The resulting plasmid was thendigested with Xcm I and Bsi WI. These enzymes result in an ˜750 bpfragment around the engineered unique restriction site. This strategywill result in the accumulation of fewer errors because the PCRgenerated sequences are smaller.

The Primers: 595 top primer (SEQ ID NO:30): 5′ -GCA GAT GTT AAC ACA CAAGGC GTT CTT CCA- 3′ 595 bottom primer (SEQ ID NO:31): 5′ -TTG TGT GTTAAC ATC TGC GGT AGC TGC TTG- 3′ 586 top primer (SEQ ID NO:32): 5′ -CAGAGA GTT AAC AGA CAA GCA GCT ACC GC- 3′ 586 bottom primer (SEQ ID NO:33):5′ -GTC TGT TAA CTC TCT GGA GGT TGG TAG ATA- 3′ Note: This constructresults in a missense mutation Glycine to Valine 552 top primer (SEQ IDNO:34): 5′ -ACA AAT GTT AAC ATT GAA AAG GTC ATG ATT- 3′ 552 bottomprimer (SEQ ID NO:35): 5′ -TTC AAT GTT AAC ATT TGT TTT CTC TGA GCC- 3′529 top primer (SEQ ID NO:36): 5′ -GGA CGA TAT CGA AAA GTT TTT TCC TCAG- 3′ 529 bottom primer (SEQ ID NO:37): 5′ -ACT TTT CGA TAT CGT CCT TGTGGC TTG C- 3′ Note: This construct results in a missense mutationGlutamic acid to Isoleucine 517 top primer (SEQ ID NO:38): 5′ -TCT CTGGTT AAC CCG GGC CCG GCC ATG GCA- 3′ 517 bottom primer (SEQ ID NO:39):5′ -GCC CGG GTT AAC CAG AGA GTC TCT GCC ATT- 3′ The outside primerswere: 5′ primer (SEQ ID NO:40): 5′ -TGC GCA GCC ATC GAC CTC AGA CGC G-3′ 3′ primer (SEQ ID NO:41): 5′ -CAT GAT GCA TCA AAG TTC AAC TGA AAC GAAT- 3′

Four clones were also generated with the RGD and 8His linkers (Example15) inserted into the 529 Eco RV site. Five 8His linkers and one RGDlinker insertion mutants were generated into the 586 Hpa I site.

The unique restriction site missense mutations at 3790-3792 (amino acid529; EcoRV) did infect HeLa cells, although at relatively low efficiency(˜1/100 to ˜1/1000 of wild-type). When the 8His epitope insert wasinserted at this site, the resulting virus had a lip phenotype (i.e., alow infectious particle).

Insertions into the unique missense restriction site at 3960-3961 (aminoacid 586; Hpa I) both 8His and RGD were both very infectious,transducing HeLa cells at least as well as wild-type virus.

EXAMPLE 18 Double Mutants

Double mutants were generated using the single mutant H3761 (Table 1) asa template. The H3761 insertion mutant does not bind heparin sulfate asassessed by both batch and column binding experiments. This mutant isinteresting because it does not infect any of the cell lines so fartested, although electron microscopy analysis suggests that this virusforms normal parvovirus shells, and by dot blot hybridization this viruspackages the viral genome efficiently.

The region of the capsid coding the sequence that contains the H3761insertion was subcloned into other insertion mutants to createdouble-mutants. The H2690 (M# 163) insertion mutant was chosen becauseit has been shown to display a poly-His insertion epitopes on the viralsurface (as assessed by using the conformational specific antibody tobind the virus to an ELISA plate and an anti-histidine antibodypreconjugated to horse radish peroxidase to detect the virus containinghistidines).

The H2690 insertion mutant helper plasmid (PACG H2690 BRDY) containingthe bradykinin insertion (Example 15) and the pACG H3761 insertionmutant were both digested with Hind III and Bsi WI. The Hind III site isin the rep gene, while the Bsi WI site is between 2690 and 3761. Thesmall fragment contains pACG H2690 BRDY while the large fragmentcontains pACG H3761.

A double mutant H2690 BRDY H3761, with the bradykinin insert inserted atthe H2690 site, demonstrated a five-fold increase in infectivity of A9cells expressing the bradykinin receptor as compared with the parentalA9 cells alone. These results indicate (1) the defect in binding of theH3761 is likely at the point of binding to cellular HS receptors, butthis virus retains infectivity if directed into cells by another route,and (2) the bradykinin double-mutant targeted entry of the virus intobradykinin-receptor expressing cells.

The H3761 insertion mutant has also been cloned into the uniquerestriction site missense mutations (Example 17), AA# 586 (Hpa I) andAA# 529 (EcoRV). The restriction enzyme NcoI lies between the H3761 andthe 529 (Glu→Ile) and 586 (Gly→Val) missense mutations, and this enzymecuts within the rep gene. By digesting the pACG2 helper plasmid containthe H3761 and the 586 and 529 unique sites with Nco I, the small Nco Ifragment (3142 bps) containing the H3761 insertion mutation and thelarge Nco I fragment (5034 bps) containing the 586 and 529 unique siteswere isolated. After ligation, the constructs with the correctorientation were established, and these clones were used to make virus.

The unique restriction site missense mutations that containing the RGDmotif (Example 15) were also used in this cloning strategy. Thus, thereare double mutants containing no inserts at the unique sites and doublemutants containing RGD epitopes at those sites.

The H3761 mutant does not transduce HeLa or CHO-K1 cells. In contrast,the 586-RGD double mutants exhibited transduction of both of these celltypes. These results strongly suggest that the transduction was mediatedby the RGD motif introduced into the 586 unique restriction site.

The double mutants with the unique restriction sites, but no inserts,and the 529-RGD double mutant did not exhibit efficient transduction ofHeLa or CHO-K1 cells.

EXAMPLE 19 MSH-Targeted AAV Vector

In one embodiment of the invention, melanocyte stimulating hormone (MSH)is used for targeting of AAV vectors to cells expressing MSH receptors.Studies have shown that this peptide will direct ligand-associatedcomplexes specifically into melanocyte NEL-M1 cells (Murphy et al.,(1986) Proc. Nat. Acad. Sci USA 83:8258), providing a convenient testsystem. For example, diphtheria toxin tethered to a 12-residue peptideencoding the MSH ligand was efficient in killing only MSH receptorexpressing cells (Morandini et al., (1994) Internat. J. Ca. 56:129).Cell death was attributed to receptor mediated endocytosis of thespecific ligand delivery.

MSH is inserted into loop 3 of the AAV type 2 capsid. In the first step,an AAV type 2 deletion mutant is made with a 12-amino acid deletion whenthe Bgl II-SpH I fragment is removed from the sequence encoding loop 3.The sequence encoding the MSH peptide is then inserted into the deletedregion.

The primer sequences to make the loop3 and loop4 insertion mutations areas follows: Loop 3 5′ top primer (SEQ ID NO:42):5-′GATACTTAAGATCTAGTGGAACCACCACGCACTCAAGGCTT-3′

The cttaag is an Afl II site, the agatct is a Bgl II site. These twosites overlap by two base pairs. The homology with the AAV sequencestarts at position 3556 and ends at 3583. Loop 3 3′ bottom primer (SEQID NO:43): 5′-CTAGCTTAAGCATGCATACAGGTACTGGTCGATGAGAGGATT-3′

The gcatgc is a Sphl site, and the cttaag is an Afl II site. These twosites overlap by one base pair. The homology with the AAV sequencestarts at position 3505 and ends at 3531 (note that this is the bottomstrand).

These primers remove 24 bp (i.e., 8 amino acids) of AAV type 2 sequencesfrom 3532 to 3555. The deleted amino acid sequence is Tyr Leu Ser ArgThr Asn Thr Pro from at amino acid 444 to 451 (VP1-Met being amino acid#1).

The 5′Sph I Afl II Bgl II 3′ sites in the sequence:5′-GCATGCTTAAGATCT-3′ result in the addition of 5 amino acids Ala CysLeu Arg Ser.

Virus is produced by standard packaging methods. The MSH-tagged AAV type2 vector is evaluated for transduction in HeLa cells and cells with MSHreceptors (e.g., melanocytes).

EXAMPLE 20 Chimeric AAV2/4 Virus-Capsid Protein Substitutions

The virions of the AAV serotypes are made up of three protein subunitsVP1 VP2 and VP3. VP3 is the most abundant subunit, it represents between80-90% of the 60 subunits that make up the virion, with VP1 and VP2making up 5-10% each of the virion. The subunits are translated from anoverlapping transcript, so that VP3 sequences are within both VP2 andVP1, and VP2 sequences are within VP1.

We have designed primers that enabled us to substitute entire subunitsand unique domains of subunits between AAV2 and AAV4. AAV4 hasproperties that are significantly different from AAV2. Thus, definingthe domains that account for these distinct properties would be ofvalue, e.g., for designing gene therapy vectors.

We have chosen a seamless cloning strategy to clone the subunits orunique domains of subunits between these two serotypes. AAV2 and AAV4top primer (SEQ ID NO:44): 5′ -TGC CGA GCC ATC GAC GTC AGA CGC G- 3′AAV2 and AAV4 bottom primer (SEQ ID NO:45): 5′ -CAT GAT GCA TCA AAG TTCAAC TGA AAC GAA T- 3′ AAV2 VP3 top primer (SEQ ID NO:46): 5′ -CGA GCTCTT CGA TGG CTA CAG GCA GTG GCG CAC- 3′ AAV2 VP3 bottom primer (SEQ IDNO:47): 5′ -AGC GCT CTT CCC ATC GTA TTA GTT CCC AGA CCA GAG- 3′ AAV2 VP2top primer (SEQ ID NO:48): 5′ -CGA GCT CTT CGA CGG CTC CGG GAA AAA AGAGGC- 3′ AAV2 VP2 bottom primer (SEQ ID NO:49): 5′ -AGC GCT CTT CCC GTCTTA ACA GGT TCC TCA ACC AGG- 3′ AAV4 VP3 top primer (SEQ ID NO:50):5′ -CGA GCT CTT CGA TGC GTG CAG CAG CTG GAG GAG CTG- 3′ AAV4 VP3 bottomprimer (SEQ ID NO:51): 5′ -AGC GCT CTT CGC ATC TCA CTG TCA TCA GAC GAGTCG- 3′ AAV4 VP2 top primer (SEQ ID NO:52): 5′ -CGA GCT CTT CGA CGG CTCCTG GAA AGA AGA GAC- 3′ AAV4 VP2 bottom primer(SEQ ID NO:53): 5′ -AGCGCT CTT CCC GTC TCA CCC GCT TGC TCA ACC AGA- 3′

These primers will result in the subunit swaps that are shown in FIG. 7.A representative coding sequence of a chimeric AAV2 capsid in which theAAV4 Vp2 was substituted is shown in SEQ ID NO:2. This sequence containsthe AAV2 rep coding sequences, most of the AAV2 Vp1 and Vp3 codingsequences, and the entire AAV4 Vp2 coding sequences and some of the AAV4Vp1 and Vp3 coding sequences in a pBluescript backbone.

The Rep68/78 coding sequence begins at nu 251 of SEQ ID NO:2, and theRep52/40 coding sequence begins at nu 923. The Rep78/52 stop signal endsat nu 2114, and the stop for Rep68/40 is at nu 2180. The capsid codingsequence starts at nu 2133 and the end at nu 4315 (Vp1 start at nu 2133,Vp2 start at nu 2544, Vp3 start at 2724).

The AAV2 sequences from the second XhoI site at bp 2420 in Vp1 to theBsi WI site at bp 3255 in Vp3 in the AAV2 cap genes was replaced withthe corresponding region from AAV4 (corresponding to nu 2350-3149 in theplasmid sequence). Briefly, the AAV2 helper plasmid pACG2 was partiallydigested with XhoI and Bsi WI releasing the 835 bp fragment. The samedigest in AAV4 resulted in a 799 bp fragment that was ligated into thedeleted AAV2 sequence to produce the helper virus encoding the chimericAAV2/4 capsid.

Virions are produced carrying a recombinant AAV genome, preferably arecombinant AAV2 genome, typically expressing a reporter gene (e.g.,GFP). These mutant viral vectors are characterized for virion formation,morphology, genome protection, heparin binding, and infectivity asdescribed in Example 15.

EXAMPLE 21 Construction of B19/AAV-2 Chimeric Vectors

Studies by Dong et al., (1996) Human Gene Therapy 7:2101, havedetermined the packaging limitations using rAAV vectors. Usingrecombinant AAV DNA templates with increasing insertions of stuffer DNA,Dong et al. determined that the packaging capacity of rAAV vectorsdeclined dramatically between 104% and 108% of wt (4883 vs. 5083nucleotides, respectively). This packaging restriction precludes the useof important genes, including mini muscular dystrophy genes as well aspromoter regulated cystic fibrosis sequences.

Accordingly, the present investigations set out to develop a B19/AAV-2derived gene therapy vector that maintains the packaging capacity ofB19, the tropism of AAV-2, as well as function as a substrate fortargeting vectors. The human parvovirus B19 (packaging capacity of 5.6kb) was chosen to utilize the major structural protein Vp2 in thegeneration of a chimeric AAV vector for packaging larger vector genomes.B19 is composed of only two overlapping structural proteins (Vp1 & 2).B19 infects primary erythroid progenitor cells using globoside as itsreceptor (Brown et al., (1993) Science 262:114). The structure of B19has been determined to 8 Å resolution (Agbandje-McKenna et al., (1994)Virology 203:106).

A chimeric AAV particle was constructed by swapping the AAV majorstructural protein Vp3 for B19's Vp2. Seamless cloning (Stratagene USA)was utilized to generate an AAV helper construct that would express allof the AAV proteins (Rep 78, 68, 52, 40 and Vp 1 and Vp2) with B19substituted for the Vp3 major Cap protein (FIG. 8; nucleotide sequencein SEQ ID NO:3; amino acid sequence in SEQ ID NO:4).

The starting material for the chimeric vector was pAAV-Ad and pYT103c.pYT103c contains the entire B19 coding domain without terminal repeats.HindIII digestion of pAAV-Ad released a 2727bp fragment which containedthe entire AAV2 capsid coding region and some flanking regions. Thisfragment was subcloned into Hind III digested pBS+(Stratagene),resulting in pBS+AAVCap. Polymerase chain reaction was used to amplifythe Vp2 coding region from pYT103c. The primers were5′-AGTTACTCTTCCATGACTTCAGTTAATTCTGCAGAA 3′ (SEQ ID NO:54) in the 5′direction and 5′-AGTTACTCTTCTTTACMTGGGTGCACACGGCTTTT 3′ (SEQ ID NO:55)in the 3′ direction. Primers to pBS+AAVCap were used to amplify aroundVp3 of AAV2. The primers were 5′-AGTTACTCTTCTTMTCGTGGACTTACCGTGGATAC 3′(SEQ ID NO:56) in the 5′ direction and5′-AGTTACTCTTCCCATCGTATTAGTTCCCAGACCAGA 3 (SEQ ID NO:57), in the 3′direction. Six nucleotides from the 5′ end of each primer is an Eam 1104I site, this site digests downstream from its recognition site in thiscase the overlap is an ATG and its compliment and a TAA and itscompliment. This site is utilized during the seamless cloning strategy(Stratagene). Digestion of B19-Vp2 and AAV2 PCR products with Eam 1104-Iand cloning resulted in a subclone of pBS+AAVCap with Vp2 of B19substituted for AAV2 Vp3. This vector was digested with Hind III andcloned back into pAAV-Ad and orientation determined resulting inpAAV/B19-Ad (SEQ ID NO:3). This sequence encodes the AAV2 Vp1 region(start at nt 1), followed by the AAV2 Vp2 region (start at nt 412), andthen the B19 Vp2 region (start at nt 607).

EXAMPLE 22 Production of Chimeric Virus

The pAAV/B19 helper construct was used in a transient packaging systemas described in Example 1. Briefly, the helper plasmids pAAV/B19-Ad andpAB11 (which contains AAV2 terminal repeats and the β-galactosidase geneunder the control of the CMV early promoter) were co-transfected into293 cells by calcium phosphate. Twelve hours after transfection themedium was changed and adenovirus dI309 (MOI-5) was added. Forty-eighthours later the cells were centrifuged and the supernatant wasdiscarded. A fraction of the cell pellet was used in a HIRT assay. Thecell pellet was lysed in cesium chloride (1.39 g/ml), sonicated andcentrifuged at 41,000 rpm for 72 hours. Fractions from the cesiumgradient were recovered and samples from each were used in dot blothybridization to test particle number of virus. The dot blots wereprobed with β-galactosidase gene, and particle numbers were determinedby control amounts of the β-galactosidase gene. Peak fractionscontaining virus were dialysed against PBS, 20% glycerol.

EXAMPLE 23 Infection of Cells with Chimeric Virus

Forty-eight hours post-transfection, cell lysates were generated andtested for transduction into various target cells. A transducing titerof 2×10⁶ was generated. Various volumes of virus were added to 293, RT-2rat glioma, U-87 glioma, as well as to two primary human glioblastomacell lines in small volumes of medium. Virus was also added to UT7megakaryoctye cells that had been incubated in the presence oferythropoeitin (EPO) for several weeks. Exposure of UT7 cells to EPO isknown to render these cells permissive for B19 infection.

Adenovirus was also added to the cells at an MOI of 5. Two hours afterinfection the virus was washed off and fresh medium was added.Twenty-four hours post infection the cells were washed with PBS, fixedin formaldehyde/gluteraldehyde, and stained with X-gal. Twelve totwenty-four hours later the number of blue cells was determined bycounting ten fields.

Transduction was obtained in the glioma and primary human glioblastomacells. Efficient transduction was not observed in 293 cells (a cell typetypically infected with AAV). Interestingly, transduction was seen withthe UT7 cells. These results suggest that the chimera has lost thenative AAV tropism and has acquired the B19 tropism for erythroid cells.This virus is characterized to determine whether it has retained theantigenic properties associated with the AAV2 serotype.

The B19 globoside binding region (loop 4 between amino acids 399-406 ofthe Vp2 subunit; Brown et al. (1993) Science 262:114) of this chimericvirus is deleted, modified or swapped out to reduce or completelyeliminate the B19 tropism for erythroid cells.

EXAMPLE 24 Characterization of B19/AAV Chimera

The results from Example 23 indicate that a transducing chimeric viruswas successfully generated. The chimeric virus was further evaluated fortotal particle yield and integrity. The remainder of the vectorpreparation was gradient purified, and the chimeric virus was analyzedby dot blot analysis to determine a particle titer of 1×10⁸ and EManalysis (see Example 6) to determine if a correct icosahedral structurewas formed (FIG. 9). From this analysis, it was confirmed that thechimeric virion that was generated retained the typical parvovirusstructure and was stable to physical purification step such assonication and CsCl₂ gradient centrifugation. This is an importantobservation since most parvovirus are heat stable (resistant up to 65degrees), resistant to detergents (0.5% SDS) and can tolerate extreme pHchanges (viable between pH of 2.0-11).

In addition, EM analysis yielded unexpected results (FIG. 9). Virionparticles of two different sizes were observed (a 23-28 nm particle,typical for wt AAV, and a 33-38 nm particle, never before identified).Further analysis suggested that the AAV 33-38 nm particle was formed bychanging the triangulation number from T=1 to T=3, resulting in largerparticles containing 180 copies of the major capsid component instead of60. These surprising results indicate that a virion structure largerthan wt AAV has been generated. This virion may have the potential forcarrying larger than wt vector templates. The larger 33-38 nm particlewill be useful in increasing packaging limits above the 6 kb range (theB19 25 nm particle packages 6 kb of DNA).

EXAMPLE 25 Packaging Capacity of B19/AAV-2 Chimera

To quantitate the packaging capacity of the chimeric virus from Example21, a series of vectors developed by Dong and coworkers, (1996) HumanGene Therapy 7:2101, is utilized with genomes of progressively increasedsizes having inserts between 745 and 1811 bases (for a maximum totalgenome size of 6.4 kb). Small-scale production of chimeric recombinantvirus is used to assay packaging efficiency by testing the DNA contentof the virus using Hirt assay, and by chloramphenicol acetyltransferase(CAT) reporter assay.

EXAMPLE 26 Construction of Other B19/AAV Chimeras

Other chimeric B19/AAV capsids are generated as in Example 21 (e.g.,swapping AAV Vp1 or Vp2 with B19 Vp1) and are characterized as describedin Examples 22-25 above. In particular, both B19 Vp1 and Vp2 aresubstituted into an AAV Vp1 chimera to generate a novel chimeric capsidcontaining AAV Vp1 and B19 Vp1 and Vp2.

These chimeras are assayed in 293 (typically infected by AAV) anderythroid cells (the cell type typically infected by B19) fortransduction efficiency and are assayed for packaging recombinant AAVvectors with increasing sized inserts as described above.

If desired, the B19 globoside binding region (loop 4 of Vp2 betweenamino acids 399-406; Brown et al (1993) Science 262:114) of thesevectors can be deleted, modified or swapped out to remove the B19tropism.

EXAMPLE 27 Loop Swaps Between AAV Serotypes

The capsid gene of AAV2, in the helper vector pACG2, was digested withthe enzymes Asp718 and Bsi WI. Bsi WI has a unique site in the AAV2genome at position 3254 bp, and Asp718 digests the genome twice at 1906and 4158 bps (AAV2 sequence numbers). The capsid coding domain of AAV2was partially digested with Asp718 and the full length (single cut)fragment was isolated. This fragment was then digested with Bsi WI andthe 7272 bp fragment isolated. This fragment removed the 904 bp fragmentthe contains the coding region of the VP3 loop 2, 3, and 4 domains.

The capsid gene of AAV4 was digested with Asp718 and Bsi WI tocompletion and a 928 bp fragment from 3284 bp (BsiWI) to 4212 bps(Asp718) was isolated (AAV4 sequence numbers). This AAV4 fragment codesfor a region in VP3 that contains loops 2, 3 and 4. The 928bp AAV4fragment and the 7272 bp fragment from pACG2 were ligated and cloneswere identified.

These clones were used to make a chimeric virus that contained mostlyAAV2 and part of the VP3 domain of AAV4. This virus did not infect HeLacells as determined by blue stained cells (viral infected cellsexpressing the LacZ marker gene). However, like AAV4 these cellsinfected COS7 cells at a low titer of 1×10⁵ transducing units/mL. Thesevirions are not recognized by the AAV2 monoclonal antibody B1.

Chimeric virus was also made in which Vp3 Loops 2-4 from AAV2 weresubstituted into the homologous region of the AAV4 capsid.

The AAV3 capsid coding region containing the VP3 loops 2-4 domains werecloned into pACG2 in the same manner as described above for AAV2/4 loopswaps. These chimeric AAV2/3 virions bind heparin agarose and infectHeLa and 293 cells. Furthermore, these virions are recognized by the B1monoclonal antibody.

Likewise, using the techniques taught above, Vp3 loops 2-4 from AAV5 aresubstituted for loops 2-4 of AAV2.

Furthermore, single loops (e.g., loop 2, 3 or 4, or loops 2-3 or 3-4)are substituted from AAV3, 4 or 5 into AAV2 or vice versa.

These mutant viral vectors are characterized for virion formation,morphology, genome protection, heparin binding, and infectivity asdescribed in Example 4-7.

A representative helper plasmid encoding a chimeric AAV2/3 capsid isgiven in SEQ ID:5. This sequence contains the AAV2 rep coding sequences,most of the AAV2 capsid coding sequences, with the exception that loops24 from the AAV2 Vp3 subunit were replaced with the corresponding regionfrom AAV3, in a pBluescript backbone. The Rep 68/78 coding sequencestarts at nu 251, and the Rep52/40 coding sequence starts at nu 923. Therep coding sequences end at nu 2114 for Rep78/52 and at nu 2180 forRep68/40. The cap coding region starts at nu 2133 and ends at nu 4342(Vp1 start at nu v2133, Vp2 start at nu 2544, Vp3 start at nu 2739).

Briefly, both AAV2 (pACG2) and AAV3 helper plasmids were digested withBsi WI and Asp 718. This removes a 904 bp fragment in the AAV2 genomefrom nu 3255 to 4159. In the AAV3 genome, the same digestion removed 907bp from nu 3261-4168. This 904 bp fragment was ligated into the deletedAAV2 helper to result in the helper given in SEQ ID NO:5 (AAV3 sequencesat nu 3184-4092 of the plasmid).

EXAMPLE 28 Hybrid Viruses

Primers were made to create a unique Hind III site in the AAV4 rep genethat overlapped the Hind III site in AAV2. In addition, at the 3′ end ofthe rep coding sequence, a unique Not I site was created 3′ of thepolyadenylation site. A virus purchased from American Type CultureCollection (ATCC) as the template for the PCR.

The 5′ portion of the AAV2 rep gene from the Xba I site to the Hind IIIsite was subcloned into pBluescript. The Hind III-Not I PCR digestionproduct was then cloned into the pBluescript containing the 5′ rep genedigested with Not I and Hind III. Primers: AAV4 3′ Not I primer (SEQ IDNo:58): 5′ -AAG CGC CGC GGC CGC TGC TTA TGT ACG CA- 3′ AAV4 5′ Hind IIIprimer (SEQ ID NO:59): 5′ -GAC GCG GAA GCT TCG GTG GAC TAC GCG- 3′

This cloning strategy resulted in a helper plasmid that is a hybrid forAAV2 and AAV4 rep genes and contains the AAV4 cap genes. This helpercontains the AAV2 rep gene up to the Hind III site and from this pastthe polyadenylation site the sequences are derived from AAV4.

This virus packaged a recombinant AAV2 genome with AAV2 ITRs. Thishybrid AAV2/4 virus exhibits the binding characteristics of AAV4, e.g.,it does not bind HS and transduces AAV4 target cells that are nottypically permissive to AAV2 transduction.

The hybrid AAV 2/4 helper plasmid is as given in SEQ ID NO:1. Thissequence encodes the AAV2 rep genes and AAV4 capsid in a pBluescriptbackbone. The Rep 68/78 coding sequence starts at nu 251, and theRep52/40 coding sequence starts at nu 923. The rep coding sequences endat nu 2120 for Rep78/52 and at nu 2183 for Rep68/40. The cap codingregion starts at nu 2123 and ends at nu 4341 (Vp1 start at nu 2123, Vp2start at nu 2547, Vp3 start at nu 2727).

Using the same techniques, a hybrid AAV2/3 virus in which a recombinantAAV2 genome (with AAV2 ITRs) is packaged. The resulting hybrid virus isviable and efficiently transduces AAV3 permissive cells.

In addition, in contrast to a recent report (Chiorini et al., 1999) J.Virology 73:1309), the techniques described above have been used toproduce a hybrid AAV2/5 virus in which a recombinant AAV2 genome (withAAV2 ITRs) is packaged within a AAV Type 5 capsid. This virus ispackaged relatively inefficiently, but the resulting particlesdemonstrated transduction of cells.

Although the foregoing invention has been described in some detail byway of illustration and example for purposes of clarity andunderstanding, it will be apparent that certain changes andmodifications may be practiced within the scope of the appended claimsand equivalents thereof.

1. A chimeric virus particle comprising: (a) a chimeric adeno-associatedvirus serotype-2 (AAV2) capsid comprising a chimeric capsid proteincomprising at least one capsid region from AAV1; and (b) a nucleic acidcomprising 5′ and 3′ AAV inverted terminal repeats and at least oneheterologous nucleotide sequence, wherein said nucleic acid is packagedwithin the chimeric parvovirus capsid.
 2. The chimeric virus particle ofclaim 1, wherein said at least one heterologous nucleotide sequenceencodes a protein or peptide.
 3. The chimeric virus particle of claim 2,wherein said protein or peptide is a therapeutic protein or peptide. 4.The chimeric virus particle of claim 3, wherein said protein or peptideis dystrophin or a mini-dystrophin.
 5. The chimeric virus particle ofclaim 2, wherein said protein or peptide is an immunogenic protein orpeptide.
 6. The chimeric virus particle of claim 1, wherein said atleast one heterologous nucleotide sequence encodes an untranslated RNAsequence.
 7. The chimeric virus particle of claim 1, wherein said AAV1capsid region is inserted into the chimeric capsid protein but does notreplace a region of said chimeric capsid protein.
 8. The chimeric virusparticle of claim 1, wherein said at least one AAV1 capsid regionreplaces a region within said chimeric capsid region.
 9. The chimericvirus particle of claim 1, wherein said at least one AAV1 capsid regionis a loop region of the major Vp1 capsid subunit.
 10. The chimeric virusparticle of claim 9, wherein said loop region replaces a loop region inthe major Vp1 capsid subunit.
 11. The chimeric virus particle of claim1, wherein said 5′ and 3′ AAV inverted terminal repeats are AAV2inverted terminal repeats.
 12. The chimeric virus particle of claim 1,wherein said nucleic acid does not comprise the AAV cap genes or the AAVrep genes.
 13. The chimeric virus particle of claim 1, wherein anantigenic property of said chimeric AAV2 capsid is reduced as comparedwith the wild-type AAV2 capsid.
 14. A chimeric virus particlecomprising: (a) a chimeric adeno-associated virus serotype-2 (AAV2)capsid comprising at least one AAV1 capsid region; and (b) a nucleicacid comprising 5′ and 3′ AAV inverted terminal repeats and at least oneheterologous nucleotide sequence, wherein said nucleic acid is packagedwithin the chimeric AAV2 capsid.
 15. The chimeric virus particle ofclaim 14, wherein said at least one heterologous nucleotide sequenceencodes a protein or peptide.
 16. The chimeric virus particle of claim15, wherein said protein or peptide is a therapeutic protein or peptide.17. The chimeric virus particle of claim 16, wherein said protein orpeptide is dystrophin or a mini-dystrophin.
 18. The chimeric virusparticle of claim 15, wherein said protein or peptide is an immunogenicprotein or peptide.
 19. The chimeric virus particle of claim 14, whereinsaid at least one heterologous nucleotide sequence encodes anuntranslated RNA sequence.
 20. The chimeric virus particle of claim 14,wherein said AAV1 capsid region is inserted into the chimeric capsidprotein but does not replace a region of said chimeric capsid protein.21. The chimeric virus particle of claim 14, wherein said at least oneAAV1 capsid region replaces a region within said chimeric capsid region.22. The chimeric virus particle of claim 14, wherein said at least oneAAV1 capsid region is a loop region of the major Vp1 capsid subunit. 23.The chimeric virus particle of claim 22, wherein said loop regionreplaces a loop region in the major Vp1 capsid subunit.
 24. The chimericvirus particle of claim 14, wherein said 5′ and 3′ AAV inverted terminalrepeats are AAV2 inverted terminal repeats.
 25. The chimeric virusparticle of claim 14, wherein said nucleic acid does not comprise theAAV cap genes or the AAV rep genes.
 26. The chimeric virus particle ofclaim 14, wherein an antigenic property of said chimeric AAV2 capsid isreduced as compared with the wild-type AAV2 capsid.
 27. The chimericvirus particle of claim 14, wherein said at least one AAV1 capsid regionreplaces a capsid subunit in said AAV2 capsid.
 28. A compositioncomprising the chimeric virus particle of claim
 1. 29. A compositioncomprising the chimeric virus particle of claim
 14. 30. An isolatednucleic acid encoding the adeno-associated virus serotype-2 (AAV2) capgenes and AAV rep genes, wherein the AAV2 cap genes encode a chimericAAV2 capsid comprising at least one AAV1 capsid region.
 31. A vectorcomprising the isolated nucleic acid of claim
 30. 32. A cell comprisingthe vector of claim
 31. 33. A cell comprising the isolated nucleic acidof claim 30 stably integrated into the genome of the cell.
 34. A methodof producing a chimeric virus particle, the method comprising: providinga cell with chimeric adeno-associated virus serotype-2 (AAV2) cap genes,AAV rep genes, a nucleic acid comprising 5′ and 3′ AAV inverted terminalrepeats and at least one heterologous nucleotide sequence, and helperfunctions for generating a productive AAV infection, wherein thechimeric AAV cap genes comprise at least one nucleic acid sequence fromAAV1 cap genes such that the chimeric AAV2 cap genes encode a chimericAAV2 capsid comprising at least one AAV1 capsid region; and allowingassembly of the chimeric virus particles.
 35. The method of claim 34,further comprising collecting the chimeric virus particles.
 36. Themethod of claim 34, wherein the chimeric AAV2 cap genes and AAV repgenes are provided by one or more transcomplementing packaging vectors.37. The method of claim 34, wherein the chimeric AAV2 cap genes and AAVrep genes are provided by a plasmid.
 38. The method of claim 34, whereinthe chimeric AAV2 cap genes and AAV rep genes are stably integrated intothe genome of the cell.
 39. The method of claim 34, wherein the AAV repgenes are AAV2 rep genes.
 40. A chimeric virus particle produced by themethod of claim
 34. 41. A method of delivering a nucleotide sequence toa cell, the method comprising introducing into a cell the chimeric virusparticle of claim
 14. 42-49. (canceled)
 50. A method of administering anucleotide sequence to a subject, the method comprising administering toa subject the chimeric virus particle of claim
 14. 51-58. (canceled) 59.A pharmaceutical formulation comprising the chimeric virus particle ofclaim 14 in a pharmaceutically-acceptable carrier.